OK, what I have is those old white plain ribbed grips on my '65 Denelt 3 speed. I want to take them off and dye them black. I cannot find proper replacements, so I want to get these off without damaging them. I have tried the hair dryer, a thin blade screwdriver, injecting soapy water, alcohol, and oil under them. None of those have worked. I figure with all that crap under them, dying them in place is no longer a good idea.

If I could find period looking replacements I would just cut them off. Any suggestions?

Find an old tool used for setting spark plug gaps and the points on REAL cars. The real thin blades will help you get under the grip and loosen it up. Squirt some WD40 in there.

Now, go to a gas station or body shop. Get an air hose with a pointed nozzle. Stick it into the end hole on one grip and plug the other with some gum and then your finger. Blow the air in there. If the seal is adequate, doesn't have to be perfect, you'll see them start to slide off. If you can get someone to help, they can twist on one while the air is going in. You have the air working to expand the grip and force it off the end of the bar.

There is a good tip on the Schwinn restoration site. I used it to remove old grips on a schwinn racer and a schwinn suburban. Basically, you pressurize the grips from one end.

https://www.bunchobikes.com/repair2.htm

I guess a photo is in order

The black is where from I tried using shoe dye. That did not work well at all, kept rubbing off. Luckily rubbing alcohol removes it easily. This are probably the cheapest grips they could find to put on the bike, now no one seems to make one like it. They are about 3.75 inches long and fit a 7/8 inch bar. The closest thing I have been able to find are copy of old Schwinn grips with the finger bumps (Pyramid). I can use those if I have to but, I want something just like these only black.

A comment to the air compressor suggestions, not a good idea with grips as old as these, it will just blow the ends out. If I want to destroy them a box knife will get them off no problem at all.

what about spray painting them black with the plastic Krylon spray paint and then a coat of clear over it?

I have a pair justlike that on my Phillips. They won't come off for nutthin. I've tried everything. Even a heat gun.
Some auto parts stores have paint for vinyl roofs on cars. maybe try that. There's also that stuff you dip tool handles in that some hardware stores have.

Make sure they will stay put when you put them back on, too. I had one slip off as I was test-riding an old 3-spd. That was the end of my old Bailen helmet. My head was fine, but the Bailen was cracked all the way through.

I was planning to use vinyl dye, but it comes in a spray can and I wanted to take the grips off to spray them. Supposedly the vinyl dye will soak into the plastic and not rub off like the shoe dye. The stuff is about $7 a can at the auto supply store. It is also supposed to smell like heck until it dries, and I do not want to leave the bike outside until that happens. Sigh, it is when you try something new that you run into problems. "A problem is an opportunity in disguise", or so they say.