In the keys to Gonia one of the couplets asks you to consider the shininess of the face but this can be a confusing thing to judge when you only have one specimen. In this mini article I have taken photos of the 2 choices to make it clear. The first thing to do is to make sure that you are looking from the front with even light.
The first photo shows Gonia capitata (but also ornata looks like this) and these are the species described as “reflective yellowish-white” while the last photo shows Gonia divisa, which is the species described as “matt orange”. Really both species have an orange face but capitata/ornata are highly dusted with reflective scales while divisa is not shiny..