A useful trick
You can’t teach an old dog new tricks. Probably untrue. Dogs and tricks go well together. It all depends. I am admittedly ambivalent about where the dog and the trick should meet; after all, not all tricks are necessary or useful. Think about it.
Sit. Stay. Down. Come. Heel. Fetch. If this sounds boring, then the dog will figure it out faster than you. Why do you think those little tidbits are so integral to the process? The dog wants to eat. No trick there.
Stand and dance. Chase your tail. Bark on my command. The dog has to keep you interested somehow, so why not throw in some behaviour that keeps you guessing. Realistically, when the dog decided play time has ended, no amount of begging will accomplish anything more than convincing the dog that you have “lost it”. Then the dog will face additional days or weeks of training you to return to handing over the little treats.
I’ve got a useful trick to suggest. Sort the socks. Our dog has figured out that the big basket full of socks is really just a toy box. Neat bundles of things that an enterprising canine can pretend are rats or other vermin. Chewable, without stressing the gums. Even tasty, if the basket contains the dirty variety. Don’t forget the challenge of separating the pairs into singles.
Since the dog can handle the separating, why not encourage the sorting as an additional exercise. I realize it will be difficult to match colours (I, too am colourblind) but if the lengths are close I won’t feel quite so silly the next time I have to show my footware in a public situation. Come on Java, get busy!