In 12th scale, purple fronts, grey rears, white rears if you want more traction, but greys are what I run. I was trying a cyan front with granite rears last time I ran 12th scale and was having good luck with those as well.
And, in touring, double pink/orange fronts, and double pink rear combo or
purple/orange (also known as plaid) fronts, and purple rear combo works also with the latter being a firmer less wearing tire, the softer ones (pink) are the faster ones, but they chunk and wear faster. Right now I am running the 2 stage tires from JACO i the double pink combo, they cost more but again they are a little quicker.