魏, 呉, 蜀, 他, and 汎 are used as symbols representing the various factions in the Three Kingdoms.
Here is what each symbol means:
魏, the blue symbol, is for the Wei faction.
呉, the red symbol, is for the Wu faction.
蜀, the green symbol, is for the Shu faction.
他, the yellow symbol, is for the Others faction.
汎, the grey symbol, is for Generic units.