Hi Wotto
I mostly get all my decal paper from here
http://www.thecopiercompany.com.au/product.asp?ID=4123the paper I used I bought from ebay,cant remember as I mainly use waterslide for aprons,etc I only used this photo adhesive paper once or twice for experiments & making up stencils.
This is how I made them (As I am slightly colour blind,I have to rely on computer colour picker in photoshop,as you know the colours are never accurate.
1) I scanned the circles using an old scanner I had and removed the lid to get the correct size.
2) You can also take a picture to help picking the correct colour.
3) I then draw the circles on a piece of paper using a protracter (that thing you used to draw circles at school) then scan these into photoshop using my permanent scanner.
4) I then redo the black line and fill the colours with photoshop.
5) These are then printed using any cheap INKJET printer onto the adhesive decal paper.
6) as you are still using the Mylar clear protectors on top,you dont need to seal the paper but I did.
7) After printing cut the circle with a steady eye and hands as well as a good sharp pair of scissors.
8) Punch out the holes required with a wad punch and apply to Playfield.
HOPE THIS ALL MAKES SENSE.