They didn't trademark a color, Sparkfun's post is misleading.
Description of Mark
The mark consists of the colors dark gray and yellow as applied to the goods. The dotted outline of the goods is intended to show the position of the mark and is not a part of the mark.
Rather, the overall "color scheme" is trademarked: grey body with yellow border. And frankly, I agree with them. That's the "Fluke look". Everyone knows that's what a Fluke DMM looks like, and everyone knows that the cheapo multimeters that also use that scheme are trying to imitate them.
Also:
Wicked burden on small business:
Trademark law is heavily skewed towards large business. Small business does not have the resources to stay abreast of all trademarks for all the products they don’t carry. If you’re going to put the onus on the little guy to avoid infringing IP then you shouldn’t need an army of consultants or attorneys to find this information. We will lose $30,000 on this shipment. But the cost of the legal legwork and manpower to make sure we don’t violate a future color seems unreasonable and simply not feasible.
That an importer has to make sure the products they import comply with local laws is nothing new. Anyone even
vaguely familiar with trademark law should have a big ol' red flag raised upon seeing that DMM. The fact that Sparkfun is importing things from a country well known for knockoffs and yet doesn't have anybody on hand who's even vaguely familiar with IP law is a bit - well, OK, unsurprising, but still,
not good.