diff --git a/bec_widgets/utils/bec_widget.py b/bec_widgets/utils/bec_widget.py
index a1c7e176..02f86975 100644
--- a/bec_widgets/utils/bec_widget.py
+++ b/bec_widgets/utils/bec_widget.py
@@ -66,7 +66,7 @@ class BECWidget(BECConnector):
         if hasattr(qapp, "theme_signal"):
             qapp.theme_signal.theme_updated.connect(self._update_theme)
 
-    def _update_theme(self, theme: str):
+    def _update_theme(self, theme: str | None = None):
         """Update the theme."""
         if theme is None:
             qapp = QApplication.instance()
diff --git a/bec_widgets/utils/colors.py b/bec_widgets/utils/colors.py
index 0cc911b2..e07d0aed 100644
--- a/bec_widgets/utils/colors.py
+++ b/bec_widgets/utils/colors.py
@@ -1,6 +1,5 @@
 from __future__ import annotations
 
-import itertools
 import re
 from typing import TYPE_CHECKING, Literal
 
@@ -71,15 +70,64 @@ def apply_theme(theme: Literal["dark", "light"]):
     Apply the theme to all pyqtgraph widgets. Do not use this function directly. Use set_theme instead.
     """
     app = QApplication.instance()
-    # go through all pyqtgraph widgets and set background
-    children = itertools.chain.from_iterable(
-        top.findChildren(pg.GraphicsLayoutWidget) for top in app.topLevelWidgets()
-    )
-    pg.setConfigOptions(
-        foreground="d" if theme == "dark" else "k", background="k" if theme == "dark" else "w"
-    )
-    for pg_widget in children:
-        pg_widget.setBackground("k" if theme == "dark" else "w")
+    graphic_layouts = [
+        child
+        for top in app.topLevelWidgets()
+        for child in top.findChildren(pg.GraphicsLayoutWidget)
+    ]
+
+    plot_items = [
+        item
+        for gl in graphic_layouts
+        for item in gl.ci.items.keys()  # ci is internal pg.GraphicsLayout that hosts all items
+        if isinstance(item, pg.PlotItem)
+    ]
+
+    histograms = [
+        item
+        for gl in graphic_layouts
+        for item in gl.ci.items.keys()  # ci is internal pg.GraphicsLayout that hosts all items
+        if isinstance(item, pg.HistogramLUTItem)
+    ]
+
+    # Update background color based on the theme
+    if theme == "light":
+        background_color = "#e9ecef"  # Subtle contrast for light mode
+        foreground_color = "#141414"
+        label_color = "#000000"
+        axis_color = "#666666"
+    else:
+        background_color = "#141414"  # Dark mode
+        foreground_color = "#e9ecef"
+        label_color = "#FFFFFF"
+        axis_color = "#CCCCCC"
+
+    # update GraphicsLayoutWidget
+    pg.setConfigOptions(foreground=foreground_color, background=background_color)
+    for pg_widget in graphic_layouts:
+        pg_widget.setBackground(background_color)
+
+    # update PlotItems
+    for plot_item in plot_items:
+        for axis in ["left", "right", "top", "bottom"]:
+            plot_item.getAxis(axis).setPen(pg.mkPen(color=axis_color))
+            plot_item.getAxis(axis).setTextPen(pg.mkPen(color=label_color))
+
+        # Change title color
+        plot_item.titleLabel.setText(plot_item.titleLabel.text, color=label_color)
+
+        # Change legend color
+        if hasattr(plot_item, "legend") and plot_item.legend is not None:
+            plot_item.legend.setLabelTextColor(label_color)
+            # if legend is in plot item and theme is changed, has to be like that because of pg opt logic
+            for sample, label in plot_item.legend.items:
+                label_text = label.text
+                label.setText(label_text, color=label_color)
+
+    # update HistogramLUTItem
+    for histogram in histograms:
+        histogram.axis.setPen(pg.mkPen(color=axis_color))
+        histogram.axis.setTextPen(pg.mkPen(color=label_color))
 
     # now define stylesheet according to theme and apply it
     style = bec_qthemes.load_stylesheet(theme)
diff --git a/tests/unit_tests/test_color_validation.py b/tests/unit_tests/test_color_utils.py
similarity index 65%
rename from tests/unit_tests/test_color_validation.py
rename to tests/unit_tests/test_color_utils.py
index eda47163..3644285d 100644
--- a/tests/unit_tests/test_color_validation.py
+++ b/tests/unit_tests/test_color_utils.py
@@ -1,9 +1,15 @@
+import pyqtgraph as pg
 import pytest
 from pydantic import ValidationError
 from qtpy.QtGui import QColor
+from qtpy.QtWidgets import QVBoxLayout, QWidget
 
-from bec_widgets.utils import Colors
+from bec_widgets.utils import Colors, ConnectionConfig
+from bec_widgets.utils.bec_widget import BECWidget
+from bec_widgets.utils.colors import apply_theme
 from bec_widgets.widgets.containers.figure.plots.waveform.waveform_curve import CurveConfig
+from tests.unit_tests.client_mocks import mocked_client
+from tests.unit_tests.conftest import create_widget
 
 
 def test_color_validation_CSS():
@@ -110,3 +116,55 @@ def test_golder_angle_colors(num):
 
     assert all(color.isValid() for color in colors_qcolor)
     assert all(color.startswith("#") for color in colors_hex)
+
+
+##################################################
+# Testing of the ExamplePlotWidget theme change
+##################################################
+
+
+class ExamplePlotWidget(BECWidget, QWidget):
+    def __init__(
+        self,
+        parent: QWidget | None = None,
+        config: ConnectionConfig | None = None,
+        client=None,
+        gui_id: str | None = None,
+    ) -> None:
+        if config is None:
+            config = ConnectionConfig(widget_class=self.__class__.__name__)
+        super().__init__(client=client, gui_id=gui_id, config=config)
+        QWidget.__init__(self, parent=parent)
+
+        self.layout = QVBoxLayout(self)
+        self.glw = pg.GraphicsLayoutWidget()
+        self.pi = pg.PlotItem()
+
+        self.layout.addWidget(self.glw)
+        self.glw.addItem(self.pi)
+        self.pi.plot([1, 2, 3, 4, 5], pen="r")
+
+
+def test_apply_theme(qtbot, mocked_client):
+    widget = create_widget(qtbot, ExamplePlotWidget, client=mocked_client)
+    apply_theme("dark")
+
+    # Get the default state of dark theme
+    dark_bg = widget.glw.backgroundBrush().color().name()
+    dark_axis_color = widget.pi.getAxis("left").pen().color().name()
+    dark_label_color = widget.pi.getAxis("left").textPen().color().name()
+
+    assert dark_bg == "#141414"
+    assert dark_axis_color == "#cccccc"
+    assert dark_label_color == "#ffffff"
+
+    apply_theme("light")
+
+    # Get the default state of light theme
+    light_bg = widget.glw.backgroundBrush().color().name()
+    light_axis_color = widget.pi.getAxis("left").pen().color().name()
+    light_label_color = widget.pi.getAxis("left").textPen().color().name()
+
+    assert light_bg == "#e9ecef"
+    assert light_axis_color == "#666666"
+    assert light_label_color == "#000000"
diff --git a/tests/unit_tests/test_multi_waveform_widget.py b/tests/unit_tests/test_multi_waveform_widget.py
index 757c5ce6..5a331f87 100644
--- a/tests/unit_tests/test_multi_waveform_widget.py
+++ b/tests/unit_tests/test_multi_waveform_widget.py
@@ -271,7 +271,8 @@ def test_multi_waveform_widget_theme_update(qtbot, multi_waveform_widget):
     palette = get_theme_palette()
     waveform_color_dark = multi_waveform_widget.waveform.plot_item.getAxis("left").pen().color()
     bg_color = multi_waveform_widget.fig.backgroundBrush().color()
-    assert bg_color == QColor("black")
+
+    assert bg_color == QColor(20, 20, 20)
     assert waveform_color_dark == palette.text().color()
 
     # Set the theme to light
@@ -279,7 +280,7 @@ def test_multi_waveform_widget_theme_update(qtbot, multi_waveform_widget):
     palette = get_theme_palette()
     waveform_color_light = multi_waveform_widget.waveform.plot_item.getAxis("left").pen().color()
     bg_color = multi_waveform_widget.fig.backgroundBrush().color()
-    assert bg_color == QColor("white")
+    assert bg_color == QColor(233, 236, 239)
     assert waveform_color_light == palette.text().color()
 
     assert waveform_color_dark != waveform_color_light
@@ -291,5 +292,5 @@ def test_multi_waveform_widget_theme_update(qtbot, multi_waveform_widget):
 
     waveform_color = multi_waveform_widget.waveform.plot_item.getAxis("left").pen().color()
     bg_color = multi_waveform_widget.fig.backgroundBrush().color()
-    assert bg_color == QColor("black")
+    assert bg_color == QColor(20, 20, 20)
     assert waveform_color == waveform_color_dark
diff --git a/tests/unit_tests/test_waveform_widget.py b/tests/unit_tests/test_waveform_widget.py
index 607a2897..d40a0f4b 100644
--- a/tests/unit_tests/test_waveform_widget.py
+++ b/tests/unit_tests/test_waveform_widget.py
@@ -484,7 +484,7 @@ def test_waveform_widget_theme_update(qtbot, waveform_widget):
     palette = get_theme_palette()
     waveform_color_dark = waveform_widget.waveform.plot_item.getAxis("left").pen().color()
     bg_color = waveform_widget.fig.backgroundBrush().color()
-    assert bg_color == QColor("black")
+    assert bg_color == QColor(20, 20, 20)
     assert waveform_color_dark == palette.text().color()
 
     # Set the theme to light; equivalent to clicking the light mode button
@@ -493,7 +493,7 @@ def test_waveform_widget_theme_update(qtbot, waveform_widget):
     palette = get_theme_palette()
     waveform_color_light = waveform_widget.waveform.plot_item.getAxis("left").pen().color()
     bg_color = waveform_widget.fig.backgroundBrush().color()
-    assert bg_color == QColor("white")
+    assert bg_color == QColor(233, 236, 239)
     assert waveform_color_light == palette.text().color()
 
     assert waveform_color_dark != waveform_color_light
@@ -509,7 +509,7 @@ def test_waveform_widget_theme_update(qtbot, waveform_widget):
     # we compare the waveform color to the dark theme color
     waveform_color = waveform_widget.waveform.plot_item.getAxis("left").pen().color()
     bg_color = waveform_widget.fig.backgroundBrush().color()
-    assert bg_color == QColor("black")
+    assert bg_color == QColor(20, 20, 20)
     assert waveform_color == waveform_color_dark