This codeblock creates a function called button-text that make use of the built-in function contrast-color in Compass. The function takes in 4 arguments in this order: Color, dark color, light color, threshold %.
So depending on what color gets written and the threshold, it will either be the dark or the light one that returns..
@function button-text($bg){ @return contrast-color($bg, #333, #eee, 50%); } .btn-a{ background: #222 color: button-text(#222); // #eee } .btn-b{ background: #aaa; color:button-text(#aaa); //#333 }