I used 3-1 for the gasket. Best to make a small batch or two, so you can get it to the consistency you need.
For an add on grip, maybe 2-1? The more cornstarch in the mix, the faster it sets up. So if you go 2-1 or 1-1, better work fast!
I imagine many types of colorants will work as long as the concentration is not too high to impede it setting up.
I have used UTC's and epoxy colorants will good results.
Do a search for Oogoo. Lots of info out there