Can the dentist ask the technical to change the veneers colours if it doesn't match by painting (dyeing) it?

I will have venners.,the front four up..when I tried them on they theyou didn't match my tooth colour.my tooth was whiter after the blech so my dentist said if the next week your tooth doesn't darken a little as it need 2 weeks for the colour to be stable we will paint your venners to be whiter and match your tooth.I didn't like the idea of changing the colour by painting it!?is it a right procedure to do in similar situation.?and will it hold the colour by time ?I don't know how venners made