Sass functions used to tint (add white to) and shade (add black to) a color.

sass-function-tint-shade.scss

// Tint/Shade for Sass
// 
// .example {
//   background-color: tint($color-var, 35%);
//   color: shade(#00cdff, 20%);
// }

@function tint($color, $percentage)                     {
                                                            @return mix(white, $color, $percentage);
                                                        }

@function shade($color, $percentage)                    {
                                                            @return mix(black, $color, $percentage);
                                                        }