diff --git a/ms2rescore/gui/app.py b/ms2rescore/gui/app.py
index 071e74b..cd13fa2 100644
--- a/ms2rescore/gui/app.py
+++ b/ms2rescore/gui/app.py
@@ -17,7 +17,6 @@
 from psm_utils.io import FILETYPES
 
 import ms2rescore.gui.widgets as widgets
-import ms2rescore.package_data as pkg_data
 import ms2rescore.package_data.img as pkg_data_img
 from ms2rescore import __version__ as ms2rescore_version
 from ms2rescore.config_parser import parse_configurations
@@ -28,9 +27,6 @@
 with importlib.resources.path(pkg_data_img, "config_icon.png") as resource:
     _IMG_DIR = Path(resource).parent
 
-with importlib.resources.path(pkg_data, "ms2rescore-gui-theme.json") as resource:
-    _THEME_FILE = Path(resource).as_posix()
-
 logger = logging.getLogger(__name__)
 logger.setLevel(logging.INFO)
 
@@ -41,8 +37,6 @@
 except ImportError:
     pass
 
-ctk.set_default_color_theme(_THEME_FILE)
-
 # TODO Does this disable multiprocessing everywhere?
 parallel_backend("threading")
 
diff --git a/ms2rescore/package_data/ms2rescore-gui-theme.json b/ms2rescore/package_data/ms2rescore-gui-theme.json
deleted file mode 100644
index 92c89cf..0000000
--- a/ms2rescore/package_data/ms2rescore-gui-theme.json
+++ /dev/null
@@ -1,155 +0,0 @@
-{
-    "CTk": {
-        "fg_color": ["gray95", "gray10"]
-    },
-    "CTkToplevel": {
-        "fg_color": ["gray95", "gray10"]
-    },
-    "CTkFrame": {
-        "corner_radius": 6,
-        "border_width": 0,
-        "fg_color": ["gray90", "gray13"],
-        "top_fg_color": ["gray85", "gray16"],
-        "border_color": ["gray65", "gray28"]
-    },
-    "CTkButton": {
-        "corner_radius": 6,
-        "border_width": 0,
-        "fg_color": ["#3a7ebf", "#1f538d"],
-        "hover_color": ["#325882", "#14375e"],
-        "border_color": ["#3E454A", "#949A9F"],
-        "text_color": ["#DCE4EE", "#DCE4EE"],
-        "text_color_disabled": ["gray74", "gray60"]
-    },
-    "CTkLabel": {
-        "corner_radius": 0,
-        "fg_color": "transparent",
-        "text_color": ["gray14", "gray84"]
-    },
-    "CTkEntry": {
-        "corner_radius": 6,
-        "border_width": 2,
-        "fg_color": ["#F9F9FA", "#343638"],
-        "border_color": ["#979DA2", "#565B5E"],
-        "text_color": ["gray14", "gray84"],
-        "placeholder_text_color": ["gray52", "gray62"]
-    },
-    "CTkCheckbox": {
-        "corner_radius": 6,
-        "border_width": 3,
-        "fg_color": ["#3a7ebf", "#1f538d"],
-        "border_color": ["#3E454A", "#949A9F"],
-        "hover_color": ["#325882", "#14375e"],
-        "checkmark_color": ["#DCE4EE", "gray90"],
-        "text_color": ["gray14", "gray84"],
-        "text_color_disabled": ["gray60", "gray45"]
-    },
-    "CTkSwitch": {
-        "corner_radius": 1000,
-        "border_width": 3,
-        "button_length": 0,
-        "fg_color": ["#939BA2", "#4A4D50"],
-        "progress_color": ["#3a7ebf", "#1f538d"],
-        "button_color": ["gray36", "#D5D9DE"],
-        "button_hover_color": ["gray20", "gray100"],
-        "text_color": ["gray14", "gray84"],
-        "text_color_disabled": ["gray60", "gray45"]
-    },
-    "CTkRadiobutton": {
-        "corner_radius": 1000,
-        "border_width_checked": 6,
-        "border_width_unchecked": 3,
-        "fg_color": ["#3a7ebf", "#1f538d"],
-        "border_color": ["#3E454A", "#949A9F"],
-        "hover_color": ["#325882", "#14375e"],
-        "text_color": ["gray14", "gray84"],
-        "text_color_disabled": ["gray60", "gray45"]
-    },
-    "CTkProgressBar": {
-        "corner_radius": 1000,
-        "border_width": 0,
-        "fg_color": ["#939BA2", "#4A4D50"],
-        "progress_color": ["#3a7ebf", "#1f538d"],
-        "border_color": ["gray", "gray"]
-    },
-    "CTkSlider": {
-        "corner_radius": 1000,
-        "button_corner_radius": 1000,
-        "border_width": 6,
-        "button_length": 0,
-        "fg_color": ["#939BA2", "#4A4D50"],
-        "progress_color": ["gray40", "#AAB0B5"],
-        "button_color": ["#3a7ebf", "#1f538d"],
-        "button_hover_color": ["#325882", "#14375e"]
-    },
-    "CTkOptionMenu": {
-        "corner_radius": 6,
-        "fg_color": ["#3a7ebf", "#1f538d"],
-        "button_color": ["#325882", "#14375e"],
-        "button_hover_color": ["#234567", "#1e2c40"],
-        "text_color": ["#DCE4EE", "#DCE4EE"],
-        "text_color_disabled": ["gray74", "gray60"]
-    },
-    "CTkComboBox": {
-        "corner_radius": 6,
-        "border_width": 2,
-        "fg_color": ["#F9F9FA", "#343638"],
-        "border_color": ["#979DA2", "#565B5E"],
-        "button_color": ["#979DA2", "#565B5E"],
-        "button_hover_color": ["#6E7174", "#7A848D"],
-        "text_color": ["gray14", "gray84"],
-        "text_color_disabled": ["gray50", "gray45"]
-    },
-    "CTkScrollbar": {
-        "corner_radius": 1000,
-        "border_spacing": 4,
-        "fg_color": "transparent",
-        "button_color": ["gray55", "gray41"],
-        "button_hover_color": ["gray40", "gray53"]
-    },
-    "CTkSegmentedButton": {
-        "corner_radius": 6,
-        "border_width": 2,
-        "fg_color": ["#979DA2", "gray29"],
-        "selected_color": ["#3a7ebf", "#1f538d"],
-        "selected_hover_color": ["#325882", "#14375e"],
-        "unselected_color": ["#979DA2", "gray29"],
-        "unselected_hover_color": ["gray70", "gray41"],
-        "text_color": ["#DCE4EE", "#DCE4EE"],
-        "text_color_disabled": ["gray74", "gray60"]
-    },
-    "CTkTextbox": {
-        "corner_radius": 6,
-        "border_width": 0,
-        "fg_color": ["gray100", "gray20"],
-        "border_color": ["#979DA2", "#565B5E"],
-        "text_color": ["gray14", "gray84"],
-        "scrollbar_button_color": ["gray55", "gray41"],
-        "scrollbar_button_hover_color": ["gray40", "gray53"]
-    },
-    "CTkScrollableFrame": {
-        "label_fg_color": ["gray80", "gray21"]
-    },
-    "DropdownMenu": {
-        "fg_color": ["gray90", "gray20"],
-        "hover_color": ["gray75", "gray28"],
-        "text_color": ["gray14", "gray84"]
-    },
-    "CTkFont": {
-        "macOS": {
-            "family": "SF Display",
-            "size": 13,
-            "weight": "normal"
-        },
-        "Windows": {
-            "family": "Roboto",
-            "size": 13,
-            "weight": "normal"
-        },
-        "Linux": {
-            "family": "Roboto",
-            "size": 13,
-            "weight": "normal"
-        }
-    }
-}