Pointless post, please search the forums before posting, so you kniw if posts like this have been posted before containing the information you need.
SSJ Hair flashes yellow when in SSJ when they power up, it never stays flashing all the time. Plus this only happens when they go ASSJ/SSJ2/SSJ3 -- never happens in SSJ1, unless you are still watching the episode when Goku turns SSJ for the first time.