Here's a typical t shirt design....lots of scribbles...and not very technical. I have to look up all the colors I want to use in a Pantone book. Each color has a number. Here's a cool place to pick colors and get their names:
http://chir.ag/projects/name-that-color/
So anyway..... I pass all the info along to my screen printer, who creates a vector (look it up) image to make it ready for print. Pretty easy, eh? It actually takes me a couple days to complete a new tshirt idea.








