I had the same conundrum, and came to this solution. I've been working on some miniatures to run battles from the mid 13th to early 14th century. From what I've gathered, this is the dawn of formalized heraldry, but there weren't standardized uniforms used by mustered troops at this time.
I built my knights around real world heraldry from the time, grouping them into color coordinated units (which wouldn't have happened historically, but makes picking them out on the table easier)
A unit of "yellow" knights:
"Red" knights:
Each knight would have brought a retinue of of men. Those men would have likely outfitted themselves so you'd have a variety of clothing and shields, with colors at their owner's whim.
For my foot soldiers, I painted some in either yellow or red livery, some in both, and the rest in a variety of neutral earth tones. For shields I painted some either solid red or yellow, solid, halved or quartered while others replicate variations of their liege's heraldry.
Together they look like this:
I'm also intending to do some units of blue and white knights along with their color associated retinues.
While individually each figure has a unique color scheme with no single uniform shared between them, together the mass takes on a unified color scheme that should make identifying them on the table easy.
That's how I do it, hope it helps!
