Transform transistor into relay / toggle switch - issues

Hello, i made a RGB LED pannel with 21 del. For the moment, those Led’s are powered by the 5v pin and everything work very well but the problem is that i would like to control those LED’s but with the same voltage . To do this, i know than i have to use a relay but i don’t have one sor i sk myself if i could use a transistor as a relay or toggle switch but after a few research and test it didn’t work.
So if someone could help me.
Thank you in advance ><

Hi,

Can you please post a copy of your working circuit, in CAD or a picture of a hand drawn circuit in jpg, png so we can see how you have configured your project. I am not sure what you mean by "i would like to control those LED's but with the same voltage"?

Tom..... :)