Callback: Decide industry colour

Decide industry colour (14A)

This callback is called when the industry is being constructed, to override the selected colour of the industry (variable A8). This colour will be used for tile sprites that request recolouring, but don't supply a recolour sprite number. The following industry variables aren't yet filled and contain random junk: 86..87, 93, 9E..A1, A9. (You probably wouldn't need to read anything but 86..87 anyway, since these fields contain information about the past, and the industry doesn't yet have a past.) Industry tiles aren't placed yet, either.

Variables A7 and A8 are filled, however, and provide useful information. Variable A7 contains the number of the funder company, or 10h if the industry wasn't funded. Variable A8 contains the number of the colour scheme randomly picked by TTD, it's between 0 and 15. If you don't want to change the colour picked by default, you can either make the callback fail or just return variable A8 unchanged.

Only the lowest four bits of the returned value are used, the other bits are reserved for future use. Those four bits are copied into variable A8 after the callback returns. You can either use industry variable 45 to get the company colour of the funder (if there's any), use a random action2 to select a random colour scheme from a given list, or of course decide on global variables like position or game year.