integra 95 problem with after market

I am trying to install an after market deck into a 95 integra and there was already a aftermarket deck in there so i pulled it out. The wires that were already there seemed like the basic colors so all i had to do was match the colors together. After connecting everything I still cant get the deck turned on. I checked the fuses and they seem fine. It seems like a common problem to me maybe im not doing something right. Any suggestions???

Tap into you're batt...red ...yellow, to pos .....................black to neg..just wanted to see if it powers up is all

Hey thanks that really helped i got it working now