ha ha.... very funny about litter-training... sometimes it's not that simple... those of us with geriatric and/or nervous kitters understand this and try to work with our pets as best we can
Let's assume that your kitty has been checked by your vet for any possible bladder infections, etc.
I have had great success with Nature's Miracle products (all enzymatic, working to break down and neutralize the chemical composition of the urine). I have treated multiple surfaces (carpet, pet beds, towels) and the fabric color has remained unchanged.
NM's Cat Urine Destroyer is a great enzymatic cleaner. Spray your clothing--or put the item in a bucket and pour the cleaner over it--and soak... I'd soak it overnight just to be sure. I then rinse the item and wash it. I've had a "soiled" cat bed, I sprayed and laundered it (All Free and Clear detergent), and the bed's owner (not the offender) returned contentedly to her bed as though it was always meant for her and never marked by another.
Regular Nature's Miracle works the same as above--I've had wonderful results.
NM's Advanced is great for repeat problem areas (in addition to "simply" removing the urine smell)--it leaves a pheremone trace behind that tells kitty he doesn't need to soil or mark this area. This product has a strong initial fragrance (not bad, just strong), but it fades fairly quickly and works truly to prevent repeat offenses--I have never had a repeat problem where this was used.
Drs Foster and Smith--catalog--has very reasonable prices for this product and very quick delivery!
Good luck to you!