Does your research involve field trips, interviewing witnesses and so forth? Or is it mainly google/YouTube based?
I do not conduct interviews, no. I do, of course, study the anecdotes collected by other researchers.
I don't go on field trips with the express purpose of seeing ufos (though I frequently look up!). In general, there is no reason to - they are too ephemeral (and are clandestine surveillance craft, besides).
So, mainly the internet then. That's fine. Lots of good stuff on the internet.
Imagine, if you will, that Earth sends Mike Tyson, Kim Jong Un and Uma Thurman as emissaries to the home of the Grays (I know, its weird, but stay with me. Its a McGuffin). The average Gray-in-the-street is likely to think they represent 3 different species. He/she has never visited Earth, as that kind of travel is the province (as on Earth) of a technically qualified and trained elite. He/she obviously recognises the overall anthropoid form, but individual features of the visitors are diverse; dark/light skin, differences in overall stature, hair, sexual features and, of course, differing eye colour and shape. Three different races. Probably at least one of them scary (Uma Thurman would be my guess).
The TV show Star Trek appeared in the 1960's and was in many ways groundbreaking in its depiction of the unified nations and races of Earth collaborating as part of a Confederation. The famous prime-time-first interracial kiss, and so forth. The stories developed, spinoffs appeared and by the mid 90's the Star Trek canon introduced us to the concept of a black character from the planet Vulcan, in the shape of Ensign Tuvok. Familiar Vulcan brain, Vulcan ears, but now he's black. Quite why Vulcan humanoids would have evolved in a parallel way to those on Earth I don't think was fully explained, but it did at least serve to increase the diversity in roles available to ethnic actors, and, as art follows society, illustrated the broadening acceptance of diversity in the population.
I'm personally unconvinced by the prospect of Grays in reality but my point is, as a cultural icon in the collective consciousness, should Jack's 90's "Gray" just be seen as an ethnic variation of the same old "alien" species.
And don't forget that none of the popular images are the product of witnesses or scientists, they are all drawn by graphic artists.