Hmmm... I think you're fine keeping the pants brown since that fits with the other two. For the upper part of his shirt, I'm not sure. I could see going a dark shade of brown and painting it like leather. Or, to keep it as cloth, maybe take the dark color of the cloth beneath it (can't tell, looks like a dark blue-grey) and mix it 50/50 with the pale blue of the guy on the left. That way it ties in with a color already on this figure and also links him subtly with one of the other vikings. That's kind of the kick I've been on recently, trying to take colors already on the figure and mix them into other portions to help create more consistency to the look. Blues, browns, and greys can all be mixed together to form some interesting desaturated colors.
Normally I go for somewhat similar colors... so a dark brown into a dark blue. I haven't experimented much with say a dark brown into a light blue or vice versa. You could try it, although coming up with shades/highlights becomes more difficult. If I've got a medium blue + a medium brown, I can shade with a dark blue mixed with a dark brown and highlight with a light blue mixed with a light brown. If I've got a dark blue mixed with a light brown... I guess I try to shade with the same dark blue mixed with a dark brown and then highlight with a light blue mixed with the light brown, but that's going to shift the colors in different ways as you go from light to dark. Anyway, this is the kind of stuff to experiment with on your palette. Mix up some colors along with shadow and highlight tones to see how they look and what you like. There's no right or wrong, it's just creating different looks and picking what you think works best for your subject.