I just got hothead pink temporary hair dye/gel ---any tips on getting the color more visible?

Bleach (with peroxide bleach not laundry bleach, OBVIOUSLY) your hair first. Then add the color. It will come out brighter and last longer.

I'm assuming you mean semi-permanent hair dye. Not that gel stuff? If you have dye, what I mentioned above will work. If you have that wash-out gel stuff, then I don't know what to tell you 'cuz that stuff sucks.