I haven’t read the study, but most of these would need a placebo group, so divide the herd into thirds, one with no paint, one with stripes, and one fully painted white to get a baseline for each group. Also would be good to randomize which group each cow goes in each day so to rule out one cow who is especially tasty to flies.
Those groups also have another characteristic that changes: the amount of the cow covered in paint.
How do you determine if its that vs the stripes or colors?
You paint a second control group the colors and patterns they already are