That looks normal for this point in the season. All of mine have begun changing color as well.

Thanks, zeedman! When they’re ready to pick, should I store them in my basement (cool) till October? I’m afraid they’re going to rot before Halloween. Should I leave them on the vine as long as possibe?

Normally, winter squash & pumpkins should be left on the vine until just before frost, unless there are signs of rot or rodent damage. This helps them to harden off, and lengthens their storage time. But I'm assuming these are Jack o' Lantern pumpkins? You could pick those any time after they have turned completely orange. The basement would be a good place to store them until October. To lessen the chance of rot, be sure to place them on a surface that does not trap moisture at the point of contact.

Pumpkins are winter squash, and can be stored for many months at cool room temperature as long as the skin is hardened and intact. Cut it from the stem with a handle left on and don't pull it off, and be careful not to nick or bruise the skin, and it'll be fine for Halloween and in fact can be kept till Valentines Day without a problem.