well, it depends how good you are matching the shade of paint
keeping in mind the old paint has aged and faded, new paint will stick out like dogs nuts

once i used fertan on a bike [mainly used it on cars],
this solution stops rust in its tracks & turns it into a black colour, once brushed on - left for a couple of hours then rinsed off with water [done], ideal for black bikes, but i reckon for any colour, its better than looking at the colour of rust and the comfort of knowing the rust wont spread