Acehnese Uniform?

So, I was looking trough some pictures from the Dutch-Aceh war, and something caught my attention: In some of the pictures, there is an uniform which appears with a curious frequency: Dark Coloured (probably blue) jackets and a local kind of fez hat.

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What would those men in uniform be? Royal Guards? Regular Infantry? Or just some acehnese nobles in fancy clothes? I need to know your thoughts on the subject.