Like how the human garrisons are recoloured for each kingdom. It'd help with the boyz if the same gesture was done to the two up to date styles.
Wc3 Warsong/Shadowmoon: Purple
Dragonmaw/BTG/Blackrock: Black
Frostwolf: Light Blue
Bleeding Hollow: Green
If choices were to be made for the colours. I feel black would get the most stretch, having the most clans and most striking clans to its name.