Fix label colors in the default Dark theme

Author: luisangelsm

YACReaderLibrary/themes/builtin_dark.json

@@ -195,9 +195,9 @@
         "labelColors": {
             "blue": "#82C7FF",
             "cyan": "#A0FDDB",
-            "dark": "#B7B7B7",
+            "dark": "#7C7C7C",
             "green": "#ADE738",
-            "light": "#CBCBCB",
+            "light": "#AFAFAF",
             "orange": "#F5C240",
             "pink": "#FD9CDA",
             "purple": "#D692FC",