fix(styles): changes success-green to be treated as a dark background color

.changeset/nasty-turtles-judge.md

@@ -0,0 +1,5 @@
+---
+'@swisspost/design-system-styles': patch
+---
+
+Changed color of text on the success background (#2c911c) to white from black for better contrast according to WCAG 3.0

packages/styles/src/functions/_contrast.scss

@@ -48,6 +48,15 @@
 }
 
 @function light-or-dark($background, $light-color: #fff, $dark-color: #000) {
+  /*
+  exception for Success-color issue #2227
+  the color is statically defined because the reference to the variable from here
+  would create a loop
+  */
+  @if ($background == #2c911c) {
+    @return 'dark';
+  }
+
   // Contrast ratio with a light color
   $contrast-light: contrast-ratio($background, $light-color);
 

packages/styles/src/variables/_color.scss

@@ -47,7 +47,7 @@ $warning: #f49e00;
 $info: #cce4ee;
 
 // Signal Colors
-$success-green: #2c871d;
+$success-green: #2c871d; /* When value is changed, please changed as well the copied value in ../functions/_contrast.scss, @function light-or-dark()*/
 $error-red: #a51728;
 $warning-orange: #f49e00;
 $success-background: #c0debb;