Mr.O has a pair of 501 which he doesn't wear as they are a shade of denim which looks quite dated (on the left) and I want to try and wash them out, not necessarily as the shade of blue he does wear (on the right), but somewhere in between - or when he thinks it's just right

How do I do that?

ETA: Specific US products may not be available to me, so I'm having high hopes from home-DIY solutions.