I change it depending on the colour of the uniform. For dark uniforms I use lighter browns and light uniforms I use darker browns:
I have used:
DARK:
Vallejo Flat Earth
Vallejo US Field Drab
LIGHT:
Vallejo: Dark Flesh
Vallejo: Leather Brown
Vallejo: German Camo Ochre
Vallejo: Red Leather
All work well... make sure the brush is old and coarse and has plenty of bristles left. Don't make the paint too - - thick is better.
Wipe the brush almost dry with a tissue before the 'splatter'
Run a dark brown wash over the shoes and around the figure's feet afterwards... replaces the shadow and definition