since this is your first multi. I wold flash between each color. what color shirt. if any thing but white i would make 1 screen for white and underbase the blue. Choke the underbase where the blue is by .5pt or 1pt depending on your presses registration abilities. 2 way you can print white, blue, black flashing each time or black, white, blue agian flashing each time the second method may give a better look and cleaner lines. The old timers may say to do the first method. I try both ways and see which I like best