well if its a young boy you can try the shoeshine method.   style their hair straight up with a strong hairspray...and shine on some bleach on the tips using a piece of foil.   Once the tips are lightened enough try using maybe the vero color intense blue...or if you have elumen available that works nice as well but I would suggest the first its bright and it holds well I used it on my husband before halloween and its still nice and bright.  Good luck...