Would this work? Mix grey & black shoe polish (seats)

[hora]

The car seats are a very dark grey but the nearest polish that I can find is a light grey. After all who buys grey leather shoes nowadays? If I mixed a tad of black into the grey shoe polish would this work?

(Worn surface on side bolster)

[hora]

I don't really want to spend ££ on cosmetics. Mechanics yes (it's a Saab Aero) but cosmetics I'm happy to do it quick n cheap really.