I'd be kinda bored if Sanji got blue flames even though it would hype up his flames being stronger. We've already seen blue flames with Marco.
Instead, I think the blue white flame with violet / purple around it would be better since it would be different from Marco's flames while still being hotter than what he originally had.
Edit: Wait I think I misunderstood and look at the numbered pictures. I thought - from the Flames picture- everyone who agreed meant was four (the very noticeably blue flame) not three.