Coloured Wool!

So I was thinking, with all the exciting new colour possibilities of wool perhaps we should have "National Colours".

Each Nation would only be allowed to use wool of their National Colours and at each of the development stages the current leader can pick an additional colour. So for example, each Nation starts with no National Colours at all and earns their first when they hit village status, their second at city and their third at metropolis.

Importantly, this encourages the trade of resources that provide the wool colours between Nations as there are many relevant resources and not all will be useful depending on the choices of Nation colours made.

It would give a very nice boost to trading indeed, but it does seriously limit any pixel art plans using more colours.
My idea to add to it would be, that once metro, each faction can design and build a big woolen flag (on a pole? On the ground? Over the nations entrance?) as a reward, using their specific colours.

True, but then pixel art doesn't really fit in the theme of any of the Nations. I thought it'd also be a good way to help add a bit more identity to the individual teams.