You began your question with a false pretext
Racism, while it is widespread now, is a relatively recent invention, of which Earth's history suggests it requires certain conditions to emerge and take root.
I can only imagine people demanding that you prove that statement alone (much less others in your question). It's false. While many people today agree that Humanity, endowed with the divine gift of Reason, should be capable of rising above racism, the truth is that Humanity in specific areas (if not in every area, some ancients rose above it) has been "racist" (meaning that one group of humans discriminated against other groups of humans) since the dawn and/or creation of the species. Consequently, your question begins by causing confusion over what, exactly, you're talking about.
Technical writing Rule #1: Never assume your audience understands you
Over the years a number of people have proverbially thrown their hands in the air and said, "my question is perfectly clear, why won't you just answer it!" Unfortunately, just because it's clear to you, the author, doesn't mean it's clear to anyone else. (Worse, it may be clear to some but not to others. Worse yet, the people who believe they understand it clearly might not....)
When it comes to a hot-button subject like Racism (or any form of discrimination), the problem is multiplied a thousand-fold. Almost everybody experiences discrimination at one time or another during their lives, which means everybody thinks they understand what "racism" or "discrimination" is. In reality, there are a great many forms of racism, a great many ways racism is imposed, and a great many consequences from racism.
Which is a long way of saying almost nobody can understand what you mean if you won't take the time to be clear and specific.
To make matters worse, you're asking a rhetorical question
Can space aliens be racist? Why even bother asking the question? It's your world, if you want them to be racist, make them racist. If you don't, then don't. If you're asking the question just to ask it, then you did a poor job because you failed to meet the expectations of the Help Center. Questions...
Must be specific and answerable: What problem are you trying to solve?
Must include context: What are you trying to accomplish? Context gives people writing answers an idea of what your end state will look like and why you want to get there.
Must include restrictions/requirements: What will make one answer better than another? If any answer is equally effective your question is not properly constrained. How can this be executed? What tech, timeline, magic or other criteria apply to the situation.
You may not agree with my assessment, but you failed to meet all three of those requirements. Not suggestions. Not recommendations. Not guidelines... Requirements.
But to be honest, all that wasn't what made me roll my eyes the most
My question is to ask how common such racist societies might be, or specifically if they would be likely to show up at all.
Are you joking? What space-faring alien life are we supposed to use as a baseline to answer that question? If we take you at your word and treat them as "human-like," then why bother asking the question? They're as likely to be racist as Humanity.