refactor: improve colors to better handle WCAG standards

Author: mrholek

scss/_variables.scss

@@ -310,8 +310,8 @@ $cyans: (
 
 // scss-docs-start theme-color-variables
 $primary:       #5856d6 !default;
-$secondary:     #9da5b1 !default;
-$success:       #2eb85c !default;
+$secondary:     #6b7785 !default;
+$success:       #1b9e3E !default;
 $info:          #39f !default;
 $warning:       #f9b115 !default;
 $danger:        #e55353 !default;