One of the trickiest things in designing a glass plate is knowing your colours and how they interact or change upon firing. Picture 2 above shows a selection of the Bullseye Glass Co. range of colours. I use Bullseye Glass Co. exclusively as they are one of the few glass manufacturers producing a range of glass for fusing and casting that is fully compatible, in simple terms this means they have a similar coefficient of expansion so they will expand and contract at similar rates. Glass that has different coefficient of expansion is likely to be incompatible and crack.
Some Bullseye colours change under temperature, this is called striking. In pictures 3 and 4 above, prior to firing, the assembled glass pieces look to be black, yellow and red. Picture 1 shows the results after firing, the yellow has become an intense tangerine.
For more about interactions between glass go to the Bullseye Glass Co. website they have an excellent range of educational information: