I'm usually a taker in this forum, but today I have something to give. I've
done similar stuff with Conditional Formatting. It's actually kind of the
reverse logic to what you want, but it gives your eye a visual queue that
Excel can also calculate off of. Conditional Formatting is under the Format
menu.
Let's say the data you want to SUMIF on is in column A. Instead of coloring
cells in column A, enter a value in the same row of column B. Conditional
formatting can be set to turn column B cells a specific color for specific
values, and SUMIF can be used to add up whatever is in column A when the
column B value on the same row is a specific value.