Nope, hips, like apples (to which they are related) come in all manners of colors. MANY factors can cause hips to either color or not. Generally, a hip is "ripe" and seeds viable approximately 110 days after pollination. If you want, you can try testing the point of abscission. You know the point on the stem where the ovary attaches to the stem and where the hips eventually break off the them? Put your thumb at that joint and grab the hip with your other fingers. Gently bend the hip while keeping your thumb firmly against that abscission point. If it separates easily, it's ready. If not, it likely isn't. There are theories which state that freezes can inhibit germination. I've never gardened in any climate "worse" than a 9b and none of the freezes my roses have ever endured have been sufficient to prevent germination. In fact, once planted, they encourage germination. if you think that flower was pollinated three months or more ago, harvest the seeds and plant them. Edit: you can also keep an eye on that point of abscission and see when it begins to seal off prior to the hip falling. When that point arrives, you can actually see it.

Thank you! I tried bending it this morning, but it feels firmly attached. We're only getting down to 30 for a few nights, so I don't think it's cold enough to do any harm. I'll leave it on until it's ready to come off, then sow any seeds there might be in there.

You're welcome! Have you any feel for about how long the hip has been on the plant. Might it be close to the 110 day mark?

I have no idea. I would only be guessing. I've only just noticed it about a month ago. It's green and blends in with the rest of the plant. It seems quite fat to me, and doesn't seem to be getting any bigger. So maybe it's getting close to the mark. I'll check on it daily now that I know it's there. I've never tried sowing rose seeds before, so I thought it might be fun.

It IS fun!