I'm not sure that I understand your question.
If I got you correctly - that's how it works, you have designated colors for each player number, just like in Stronghold Crusader. The player 1 is always red, the player 2 is always orange I think, etc... And all you can do is change crest for player 1, change crest for player 2, etc...
Now, since it works like that, the only thing which makes sense is to make the crest for player 1 to be red, for player 2 to be orange, etc... otherwise, you would have the orange player on your maps with their knights bearing green shields for example.
You simply don't have a crest for Sir William for example, but you only have a crest for player two - preferably an orange one I guess.
Now, it's still not the end of the world, you could play with Sir William and make him yellow if you wish. You just designate a certain yellow crest to the yellow player (don't know the number), pick an eight player map, pick several Williams, and kick all of those who are not yellow. Then choose your map, set everything, and have fun.
Another thing you could do is to be nostalgic, and to make all shields look like in Stronghold 1 or like in Stronghold Crusader - all with lion, or all with the cross.
I hope I answered your question.