For debug putted back os path.

So if you set debug to True in the about file, it will get the file url 
from os path. When debug is set to false, it will get it from 
sys._MEIPASS

NanoVNASaver/skins_utils.py

@@ -13,9 +13,35 @@
 #
 #  You should have received a copy of the GNU General Public License
 #  along with this program.  If not, see <https://www.gnu.org/licenses/>.
+from os.path import join, dirname, abspath
 import sys
+from .about import debug
 
-DARK_SKIN_MONOCHROME = sys._MEIPASS + '/skins/dark-monochrome.css')
-DARK_SKIN_COLORED = sys._MEIPASS + '/skins/dark-colored.css')
-LIGHT_SKIN_MONOCHROME = sys._MEIPASS + '/skins/light-monochrome.css')
-LIGHT_SKIN_COLORED = sys._MEIPASS + '/skins/light-colored.css')
+def DARK_SKIN_MONOCHROME():
+    if debug == True:
+        return join(dirname(abspath(__file__)), 'skins/dark-monochrome.css')
+    else:
+        return sys._MEIPASS + '/skins/dark-monochrome.css'
+
+def DARK_SKIN_COLORED():
+    if debug == True:
+        return join(dirname(abspath(__file__)), 'skins/dark-colored.css')
+    else:
+        return sys._MEIPASS + '/skins/dark-colored.css'
+
+def LIGHT_SKIN_MONOCHROME():
+    if debug == True:
+        return join(dirname(abspath(__file__)), 'skins/light-monochrome.css')
+    else:
+        return sys._MEIPASS + '/skins/light-monochrome.css'
+
+def LIGHT_SKIN_COLORED():
+    if debug == True:
+        return join(dirname(abspath(__file__)), 'skins/light-colored.css')
+    else:
+        return sys._MEIPASS + '/skins/light-colored.css'
+
+DARK_SKIN_MONOCHROME =  DARK_SKIN_MONOCHROME()
+DARK_SKIN_COLORED = DARK_SKIN_COLORED()
+LIGHT_SKIN_MONOCHROME = LIGHT_SKIN_MONOCHROME()
+LIGHT_SKIN_COLORED = LIGHT_SKIN_COLORED()