how long should i wait?

i tried to dye my hair last sunday to golden blonde with a box kit. However after i mixed the chemicals, something came up and i couldn't put it in right away. It wasn't until a half hour later that i put it in. There was essentially no color difference. I heard that the stuff becomes basically useless 30 mins after mixing the chemicals. So how long should i wait to try and dye it again? Is it going to fry my hair if i try it within a week?

You can go ahead and do it at any time.  The developer portion of the chemicals pretty much was already past its chemical reaction and didn't do anything.  You didn't cause any damage and you can go for it at any time.

Out of curiousity, what is your color now and what are you going to?

If your hair is in good condition you can leave it for a week then re-apply another colour. After leaving the colour in open air for 30 mins the chemicals break down and therefor the colour will not penetrate through the hairs cuticle giving the desired colour.