Butternut squash question

I've got a lot of butternut squash growing, and the rinds are turning that beige color. It's been a ridiculously rainy year this year and I'm worried about them rotting in the field. What's the soonest I can bring them in without risking loss of flavor and storage ability? Will they be ok as long as the plants are green and growing? Should I put something under them to keep them from rotting underneath? Right now they're on straw (mulch).

I believe you want the stem to be cracking a bit, indicating that the plant is drying out and not still pumping moisture into the fruit.

If you set the fruits on flat rocks, that will help them to mature more quickly, and prevent any rot issues.

They are safe to harvest and store when they are completely beige all the way around and the skin is hard enough to resist trying to jab a fingernail into it. Be sure to clip them with a small piece of stem attached....if any break off at the squash be sure to use these first. If your weather was drier, yeah, it would be safe to leave them on the vine longer, but as you say the danger of rot, not to mention critters, is more the longer they stay out there....

My test method is the fingernail. If your fingernail does not leave a dent, it's ready to harvest.
The squash may not be fully beige all the way around, but should be at least mostly beige. Green skin will be softer which allows damage which then allows decay.