Tsetse flies are known to avoid zebra stripes, too. When you go to the Serengeti....wear white. It seems to repel them equally well.

Years ago a buddy of mine had a Kaw 900 that was painted like a Holstein, and boy did it moooove. By the way I read the same article kind of interesting.

. . . also, this :
[amazon.de]

. . . on a (somewhat) related note :
[phys.org]

Maybe not a shoo-in, more of a moo-in. Could not resist. Alright - say it works, what are the costs to keep painting the cows? There are a number of different cow breeds with multiple markings. Possibly some of those breeds are less susceptible. Too much brain thought on this topic at this point.