Painting some GP40-2

Hi..

I have just pick-up 3 Athearn GP40-2 and wish to re-paint them in the Frisco Red and White.

I was wondering what is the best/right coulor red to use. Do I paint the shells white, mask off and paint the red or vise-a-versa.

What decal set do I need to order. Also what detail part could I use to detail them.

Thanks in Advance
Stuart Mitchell