Well, obviously, all we can do is speculate...first on the various races, and then second on their agendas... So, rather than try to affirmatively
answer your question, I'll just list some of them, and their most coinciding goals...(note, this is just a mini compilation, others feel free to add,
also, it's not my personal opinion necessarily)
Greys-genetic automatons of the Greens...serve as their "yes men" and "go to" boys... They are primarily responsible for abductions, and are the
US' primary race of contact and cooperation...though there have been disagreements....and altercations. They serve on scout-type ships, and on the
larger motherships, but as servants of the Greens.
Greens-creators of the Greys, and their directors...
Pleidians-Nordic looking aliens, seem to be somewhat concerned for our welfare, but distant, and not too cooperative...limited interaction with the US
government...and last contact was decades ago (officially)
Reptoids-two schools of thought here.... One, the Icke school, that they are subterrainean aliens, that may have always been here, and two, that they
are the enemies of the Greys and Greens....and are openly more hostile than the Greens and Greys.....
Blues-more scholarly, and another common abductor, similar to Greys, may be simply another genetic adaptation by the Greens....
There are far more, and with other stated goals... I'd suggest searching the internet for the "Yellow Book" or Lear Letter, or even the Krill
Again, this stuff is out there, but supported by numerous sources, so take it with a grain of salt.....