Oh yes, you're very wrong in that regard. Chroma is needed for a multitude of things here, using your Stand is just part of it.

[ His hand still hadn't moved, waiting for Johnny to take it. Consider it good faith or something, that's how he would say it if pressed further. ]

It's currency and it's power, without it you're little more than useless crystal statue. Take my hand, don't just stare at it.

[ Okay, so he couldn't be that passive about it. ]