is it possible to make a different color tail (like black with firetail) with the plastic molds from lurecraft? and what do the molds look like?

Yes, it's not that difficult. You just need two melting pots and after a little practice you'll learn how hot or cool the first pour needs to be before adding the second. You can do it with one or two piece molds.

SE Kansas grass grower

Yes it is possible, it is easy with a one piece mold. Pour the body then the tail. I do it a lot, it takes a little practice but works.
As ring fry said you need 2 pots are a necessity.

Yes you can do it with the lure craft mold's, that's all I use, and as stated above, you will need to pots, also both plastic color's need to be hot so that they will blend togather where the two colors meet.