To get blues(any breed) you need at least one bird already having the blue gene. For the "solid blues" you want solid black birds also as Blue is a gene that dilutes the black to blue.. So every blue bird you see is really a black chicken with a blue gene. BTW a Splash is simply a black chicken with two(or pure, if you want to look at it this way) blue genes.
So if you have or are going to buy birds, you need at least one Blue or Splash and/or Black birds.
A blue and a black will give you half blue and half black babies.
A splash crossed with black will give you 100% blue babies.
Blue x blue= 1/2 blue, 1/4 black, 1/4 splash babies.
It does not matter which parent is which color by the way
A lot of people get confused by "white" in regard to blue breedings. The "white" mentioned in this kind of breeding are actually Splashes(usually a mostly white or tinted white with flecks of black), not the white as in white leghorns, white rocks etc as this white is due to completely different genes. White cochins and white giants should be regarded as just that- white. I believe cochins and giants have the recessive kind which would mean a white giant or cochin crossed with black would produce all black chicks.