fix: several themes have poor contrast for "blue" colors

Mirage, Onyx, Tutatara

Author: starpit

plugins/plugin-codeflare/web/scss/themes/Mirage.scss

@@ -36,5 +36,6 @@ $color-red: #eb5b8e;
 $color-cyan: $latency-1;
 $color-yellow: #e7c484;
 $color-purple: #a38aa7;
+$color-blue: $latency-0;
 
 @include Theme($Theme);

plugins/plugin-codeflare/web/scss/themes/Onyx.scss

@@ -34,5 +34,6 @@ $latency-5: #929292;
 
 $color-red: #c83b22;
 $color-cyan: $latency-0;
+$color-blue: $latency-1;
 
 @include Theme($Theme);

plugins/plugin-codeflare/web/scss/themes/Tuatara.scss

@@ -35,7 +35,7 @@ $latency-5: #9db5dd;
 
 $color-green: #bcc48c;
 $color-red: #cd8155;
-$color-blue: #9db5dd;
+$color-blue: color.scale(#9db5dd, $lightness: 20%);
 $color-cyan: #9dd5dd;
 $color-yellow: #cdb67f;
 $color-purple: #c48cbc;