That's not racists at all, that's just a person's personal preference for what they find attractive, and it often can't be helped.
We develop our models of what we find attractive early in our development by what we are exposed to.
It scares me a little that you don't know this, yet feel confident enough in your knowledge to type out these words.
Is it racist if I only like blonds? No, but that does rule out more than a few races of people that can't naturally grow blond hair. You're allowed to have physical preferences for certain traits. What you shouldn't do though is treat people differently because they don't have those traits that you value.
What would be racist is if I said I only hire [insert race], or I only let [insert race] people rent my condo.
so back to your example - if you only liked blonds, and exclusively date them, then are you not treating other potential dates "differently" (in the sense that you do not date them or even give them as chance)?
People can like whoever they want to like. Some people may only like those of a certain height, weight, race, class, and any other attribute you may want to think of, but it is not necessarily wrong. It is up to each individual to have the freedom to date whoever they wish.
You might be conflating this with the societal denigration of certain races or classes, which is surely bad because there really is no reason to denigrate them, but that is not the same as saying everyone must be attracted to those of any combination of the above such factors.