I would go against any blue, red, purple, etc colors. Police, fire, emergency, etc have the only legal use.
I personally don't care for the halos and all that which people do and drive with. My friend received a fine for his annoying "blue" fog lamps
If you stay with a white or amber you will be fine with whatever way you choose.
I did that to my old Volvos. The fender marker was not a US option, but I added it and wired them to stay on, and activate with the turn signal as well.