As above, the infantry and cavalry wore the same colour uniforms.
I also use English Uniform for my British, although WW1 khaki was a distinctly greener shade than the WW2 variety. Whatever, maybe they have spent too long in the mud.
Early war German uniforms were distinctly grey, I just used a mid grey (Humbrol Sea Grey iirc), later in the war they were more like WW2 Feldgrau, but by then most of the German cavalry were fighting as infantry anyway. I do have a regiment or so of late war cavalry in steel helmets, most most of them are Uhlans.