put them in a paper grocery bag with a ripe banana. they will turn
The problem with this is that they really shouldn't. Capsicum spp. does not have an ethylene hormone pathway for maturation, which is exactly what we're trying to achieve when putting unripe fruit in close contact with ripe fruit (which leaks ethylene gas to the immediate atmosphere). Yes really, this is how this trick works!
However, if the fruit is immediately picked the cells should still "be alive". It's not unreasonable, as far as I know, to expect the maturation to continue at a well lit window sill or something. But YMMV since I've not tried experimenting or researched this further.
Edited by SwedishGhost, 15 October 2017 - 08:35 AM.