The current ess files use hexadecimal values for the colors in the prototype. We need to change those to Less variables, as they are repeating throughout the UI.
It would be best to use the existing color scheme, see
It would be great if we could use the proposed built-in Less variables but they don't seem to be in core just yet (see https://github.com/wikimedia/WikimediaUI-Base)
Instead, we should just make sure all the repeated color values are defined as Less variables and then used in the definitions.