The colour of Hummingbird feathers is by & large not due to constitutional pigment but is due to refraction & diffraction of the incident light as a consequence of the feather's micro-structure.
In practical terms this means that Hummers are best photographed in direct sunlight or by flash. If flash is used the ideal setup is to use 3 or 4 flash units positioned in an arc around the Hummer with the principal flash activating the slave units which should themselves be set to reduced output. Such a complex setup clearly requires nectar-baiting & needs artistic skill to prevent the final image from looking contrived -well beyond the skills of this photographer!!!