Once we know which colours we need made (which should be in one of the other threads I guess, but as a starting point let say R/G/B/Smoke), I'd suggest that (only) selling complete sets containing all of them might make a lot of sense;

1). We wouldn't have to fuss around with individual quantity estimation or minimum quantities for the less popular colours. Once we know how many sets we're likely to need we just order that many in each colour.

2), Many people might want multiple colours anyway - who knows what cars we might be driving next year?

3). Caster is more likely to come through on the order. An order for 200 sets of four colours is going to be more attractive than an order for 75 blue, 50 red, 30 green and 45 smoke. And more likely to be produced correctly.

4). We automatically oversupply the market, and in doing so add some insurance for those people who miss the boat. People will have spare colours laying around and in a couple of years time when someone urgently needs a sset of smoke buttons they will be more likely to find someone willing to sell them some.

5) From what's been posted before, the startup fixed costs are far more significant than the per-button costs. Getting 200 sets of 4 colours made is not going to cost much more than getting 50 of each colour to sell individually. A complete set for $30 is going be more attractive to us than a single set for $25.