Any of the horned species can be sexed at birth. They have something called ‘horn buds’ were the horns will start growing. They look like enlarged scales with a ring of smaller scales around it and you can see them if you look closely. You might need a magnifying glass?
Here are the horn buds on a baby male Trioceros deremensis:
Here is the horn bud on a baby female Trioceros werneri: