Does this always return a valid ICompoundProperty?

This should be its own function.

The code in both if block is exactly the same, except for the variable type. This can be abstracted into a templated function.

Here you can flip the conditions and return early.

if (!typedGeomParam::matches(prop_header)) {
  return false;
}

typedGeomParam color_param(arbGeomParams, prop_header.getName());
return color_param.valid() && !color_param.isConstant();

Given the parameters, it's no longer given that this is related to colour at all. Probably it's better to rename color_param to geom_param.

has_animated_... reads more naturally.

There is no guarantee that this function will only pick up on animated vertex colors, though. There could be other IC3fGeomParam or IC4fGeomParam that cause the function to return true. This should be reflected in the name of the function.

I don't see how an ICompoundProperty can be nullptr. Maybe you mean to call .valid()?

No else after return.