I want to paint the wall surrounding our fireplace. Let me explain my situation;All four walls will be painted a light yellow, the forth wall around a dark manteled fireplace is where I want to paint color blocks using three shades of blue, light, medium and dark. In between the blocks will be light yellow about an inch or so wide. I actually have three questions:
1.) The wall I want to paint with the shades of blue is currently a nasty green color, I know I'll have to use a primer such as Killz or Zinsser, should I apply another coat of primer under the 'color blocks' to assure the light yellow doesn't discolor the blue?
2.) I'm thinking I can achieve the look I 'm striving for using painter tape. How can I assure the color will not 'feather' into the yellow or visa versa?
Thanks

A second coat of primer is not necessary since you could do a secopnd coat of blue if you see a problem when you are done. 3M blue painters tape should serve you well. Make sure your edges are fully adherering by rubbing the edge with the bottom side of a spoon. What are your wall surfaces made from, drywall?