I have a series of Baetis patterns that I use from the start of June, and for about three weeks. The colors are subtler, and I use more grey than olives in my dubbing mix. The colors of the first and second generation hatch are different in my waters (mostly Hedmark, Norway). The first generation being lighter and more grey, whereas the second generation of the bug have darker olive/brown olive tones.
I guess the color combinations are a matter of taste. You mix the tones you believe in. This is one of the spring tones of my choice. It’s really an adaptation of the Adams grey, mixed with a pale olive dubbing in a 60-40 ratio with the overweight on grey.