Can tattoos hide my cafe au lait spots?

Possibly. It depends. If you are going to get some ornamental tattoo then it could possibly hide your spots. However, if you are considering tattooing your spots individually to "fill them in" then, technically yes, it might work. The trouble will be in getting the tattoo ink to match your skin color. And when your skin tans (if you tend to tan) the tattoos will not darken. Hope this helps.
Why do you ask? Most people who like someone also like their distinguishing features, including such common birthmarks as cafe-au-lait spots. If somebody has tried to persuade you that they are unattractive or that you are supposed to dislike them, ignore that person and do your own thinking. Even if they are a marker for illness (neurofibromatosis), hide them only if you truly wish to do so.