During the feudal period it became common for foot troops to have tabards & shields in basic colors. These might be the leaders colors, knight, lord, etc. Or the colors of their city. town, or if they are fighting with a martial order(religious or other). Footmans shields would be very basic, probably just 2 colors in a simple design. Divided 1/2&1/2, a cross, a saltern, bands of 1,2,or3, piles, chevrons, etc.