Oh this is easy since one of them just dyed their hair. Just start talking to one of them, the other will be listening anyway.
You: "Hey, I need a female opinion, is it really true that blondes have more fun?"
Chances are that she/they will start talking about the brunette dying her hair. You want them to eventually talk about the fun things they do, so bring it up if they don't. Either way, it will be natural since it will relate to your original question. Do not talk for more than 5 minutes, if you can help it.
If everything goes decent, close with a variation of "You seem cool, we should
really hang out as friends sometime, to be honest I'm already dating a couple
of girls non-exclusively and would rather not complicate things by dating
anyone else but you seem awesome so let's be friends and give me your number."
If they really are hot, then they will wonder why you didn't hit on them like the other 1000 guys in their life, and will put in effort to get your validation.
And that's how you turn the tables.