I must replace the style color with one not present in the variants. Is there a quick way to do it... maybe through css override? For example, replace the color of variant 2 from #4693DD to #1A78C4 in all instances?
Yes that right, but this is the easiest way to do this. Other is to copy all this classes to override.css and change it there. This file will be overwritten to, but since all changes should be done in this one file only than it's easier to keep this one file out of the update.