Cooking Belgian Waffles in waffle iron
I would first try cooking them longer. Raising the temp can also work, but you run the risk of burning whatever oil you are spraying onto the waffle iron, which can taste off (not a big risk) and will smoke up your home.

Without knowing about your batter, I'd suggest adding more sugar in some form. That's often the culprit in homemade pancake/waffle batters, we neglect to use enough sugar. More sugar will allow the outside to caramelize more, which is the browning you see. (Ok, it's a malliard reaction)

Browning occurs when sugars and proteins (in the flour, eggs, milk, etc) interact under high temps. So not enough of either, and you will end up with a paler product no matter what.