Change background color based on cell content from link

I have been trying to make some formula or macro that will color the
background of cell contents based on the contents. I have far more than 3
conditions so the conditional formatting is out. My data will remain
constant, meaning it will change but always have the same possible contents
within my list, but I have a list of about two dozen different possible
matches and each would need to result in a different color. I have a
reference sheet and know what the color numerical equivalent is for the
colors I want to use.

The data I will have in the cells is actually produced through a link to
another workbook so the actual value doesn't display in the cell contents. I
see the link being =workbook!a1 and I don't know how to get a formula to
recognize the contents it produces to change formatting. Once the sheet is
updated with new data from links it doesn't change, other than formatting.

My request is how do I accomplish this? Say I have contents that shows
value1, value2, value3, etc... I am fairly sure this will be a VBA macro or
formula but I just don't have the knowledge to figure it out and nothing I
find on the web is clear enough to take me from "novice" to at least a basic
understanding what to do and incorporating it into my workbook.

Thanks in advance for any help you might be able to provide!