No, it's not accurate at all in that or many other (most?) respects. The earliest evidence we have of anything even resembling uniforms in medieval western Europe appears some 600 years after the show is set. 9th century Mercia and Wessex were not centralized governments that could support a uniform, state-equipped army; most all soldiers were supplying their own gear or had been given it by a nobleman they were in service to. Tabards and surcoats and the like weren't commonly worn over armor until about the 12th century. Most men in the army probably would not have had any armor to begin with, mail being very expensive.