[fix:] color issues solved temporarily

App.axaml

@@ -1,7 +1,7 @@
 <Application xmlns="https://github.com/avaloniaui"
              xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
              x:Class="PLG_Exam.App"
-             RequestedThemeVariant="Default">
+             RequestedThemeVariant="Dark">
              <!-- "Default" ThemeVariant follows system theme variant. "Dark" or "Light" are other available options. -->
 
     <Application.Styles>