Since the definition of "white" is inherently cultural, it varies from place to place and from time to time. Today, in US and Europe, pretty much everyone who cares about racial categorization would consider Irish "white". Historically, it was different, but that is only relevant when discussing history.
Isn't it even more racist to replace them in a picture? Being told that your skin colour is too offensive to show sounds a lot worse to me than calling them "white" considering their skin is very white