For eliminating the blue, I use my regular image editing program. I use Paint Shop Pro, but most image editors have similar functions, so I will try to make this a generic description.
First, I use the select-by-color function, often called a magic wand. I select the blue areas. Then, I select my brush color. Many editors have both foreground and background color. I select a solid, pure white. Then I use the fill function, which fills all selected areas with white.
You may have to play with the tolerance setting on the magic wand tool so it selects all the backing blue including any variation, while not selecting any blues that are part of the design. I have never had any problem selecting just the backing blue after the first adjustment of the tolerance one or two times.