I think this question is too general, do you have some specific examples?
If someone is bikeshedding about what some other project that they aren't working on or going to do themselves, then: "That's a great/interesting idea, why don't you put it in an email/ticket and it can get prioritized in the context of the other deliverables for the project".
If it's about their own project/work, or how to tackle it, then: "Sure, whatever you think is a good idea, just go do it. I trust your judgement. Do it however you feel is best, let's look at it when it's done.".
Bikeshedding isn't always a bad thing (as distinct from talking too much, being all talk no action, being disagreeable / argumentative, which are). It can be used deliberately or constructively too... if someone has big project that they've spent a lot of time on, and are emotionally attached to, but you think the whole project is actually stupid or a bad idea... then you can stall it by telling them you support their goals, and want to work with them, but you just have some positive suggestions for this inconsequential aspect of their project that you'd like them to think/talk about at great length... and then will often get sucked into it, lose sight of driving their project forward, but not get upset or defensive about a confrontation.