ubase, white, red, yellow, blue (cyan?) and black. So it's doable with six colors. I would go with discharge underbase here. There is just too much of it to come out cleanly with plastisol.
You'll have to hold some fine dots, might have to go to 45lpi to keep it clean.
Make sure it goes to somebody who knows what they are doing, so Dan or Scott or some other member here that has plenty of experience.
pierre