Some people can pull if off while others look a bit off. I would see how you feel with natural brows against blond hair first. If you are not %100 comfortable with the contrast you can lighten your brows a bit. Make sure not to go too light or even the same shade of your hair for that matter. You only need 1-2 levels of lift to blend the contrast between hair and brows. Make sure to use color only and never ever use a lightener on or around your eyes.

It all depends on the tones. It can be very beautiful. My daughter is that way naturally. She had very blonde hair and dark eyes and brows.

As long as they're not drastically different (black and platinum blonde). Plus it helps if your dark roots are showing a bit.

What is your skintone like?

The contrast between blonde hair and dark eyebrows can be very stunning if it's the right shade of blonde for your coloring. I myself have dark brows and highlight my hair a golden blonde. See the photo attached. Denise Richards is another beautiful example of blonde with dark brows.

I suggest if your planning to colour your hair a really light colour compared to your eye brows then its best if you also dye your eye brows. It is a simple proccess, just don't leave the dye on too long.