[SDK] Work out logic for suggesting icon color with background change

[aaronreed708]

Problem/Concern

Mentioned by @lwnoble today as she and I discussed how background color changes would trigger checks in V2 UI (related to #1052). We need to work out and document the logic required to run should a background color change when it has an icon color defined. This logic needs to be documented in the Figma file found in #820 in the "WCAG CHANGE All colors/on colors must be recalculated..." layer.