[Refactor] Tidy up the color variables.

src-ui/app/main_page/main_section/language_selector/LanguageSelector.module.scss

@@ -46,5 +46,4 @@
 
 .language_label {
     font-size: 1.4rem;
-    color: var(--dark_basic_text_color);
 }

src-ui/app/main_page/main_section/message_container/log_box/message_container/MessageContainer.module.scss

@@ -81,7 +81,6 @@
 }
 
 .message_main {
-    color: var(--dark_basic_text_color);
     user-select: text;
     font-size: 1.4em;
 }

src-ui/app/main_page/main_section/message_container/log_box/message_container/message_sub_menu_container/MessageSubMenuContainer.module.scss

@@ -30,7 +30,7 @@
 
 .tooltip_title {
     font-size: 1.2rem;
-    color: var(--dark_basic_text_color);
+    color: var(--dark_200_color);
 }
 
 .hold_progress_bar {