drawing

I’m having a hard time to find the correct way to explain to my son in English that he went outside the pattern of the drawing (as in the picture). Should I say “You have exceeded the …”?

Thank you!

You have deviated from the outline of the pattern.

Or:

Remember to colour inside/within the lines.
You need to try and stay inside/within the lines.

(If I understand this correctly, you want to teach your son how to colour “properly”.)

Thank you Alan and Cristina.
You understood well Cristina. This is what I wanted to find out. Thank you!