I like it. I did one for the Oregon coast lighthouses and I think the data included info like range and viewing angle, so gave each light house its own specific light symbol.

But I think these are matched well to the hue changes do I can only see it in the legend. The map looks smooth.

The issue is less the quantity of hues but that they be perceptually linear. Reg rainbow ramps are terrible at this, lots misc hot bands from low to high. Even your much smoother ramp has 3 bright bands by intensity. The low, the high, and at 6.

I appreciate the enthusiasm, but the main art work is not mine to share. It appears without attribution and dif text in a few places online. I modified it obviously, but I’m not selling or distributing it for sale. Would appreciate if you removed the t shirt link.