SASS Color addition and subtraction

[goltsov]

There is a deprecation warning when compiling SASS:

The operation #A9A9A9 plus 55is deprecated and will be an error in future versions. Consider using Sass's color functions instead. http://sass-lang.com/documentation/Sass/Script/Functions.html#other_color_functions

There is a similar warning for the minus function.

Since the generated output is #e0e0e0, the addition function is adding 55 to each RGB value. This can be replaced with the sass function adjust-color(#A9A9A9, $red: 55, $green: 55, $blue: 55) source