Well Ronald to answer your first question there is no true winner in all cases. Tamiya makes some of the best armour kits on the market but they have their dogs mixed in. Dragon is very good, if you want German armour (they've been a little lax with their allied stuff). Academy has some great kits also, but avoid their old stuff like the plague. AFV Club also has their share of good stuff. And of course there's always Italeri, not the best engineering on the planet but have some kits that have stood the test of time and the price is always right.
Airbrushing is like using a small air gun to paint your vehicles. You can spray hobby enamels or acrylics without much trouble. It takes a little while to learn how but that's what there forums are about. Lots of help here.
By colour I assume you mean what kind of paint. I use Tamiya Acrylics for most of my painting. I also use Model Master Acrylics a little bit. Both of these are fine paints but I prefer the Tamiya.
Happy Modelling and God Bless
Robert