Firecrest.
I once lightened the colour of a top-end Swedish leather flightbag, right back to the basic fleshy tone of of the initial tan.
IIRC, I used a handy ,cheepo, bulk bottle of nail varnish remover and balls of cotton wool.
The dye came off very easily with no smears and dried off very quickly.
I have also used Meths on other items, but the results are variable.
Neither, probably , is the ideal fluid to use with leather, but I did nail varnish remover job some 26 years ago and I still use the flightbag, its never fallen to bits....just got better looking with age.
Ceeg