Absolutely, brown mascara can be a great choice for blondes. The color theory behind this is that brown, being a softer shade than black, can complement lighter hair colors, such as blonde, more naturally. It can provide a softer, more subtle enhancement to the lashes, which can be ideal for a daytime or casual look.

From a chemical perspective, the pigments used in brown mascara are typically iron oxides, which are safe for use around the eyes. These pigments are less intense than the carbon black used in black mascaras, resulting in a less dramatic effect.

However, the choice of mascara color can also depend on the individual's skin tone and eye color. For instance, if you have a cool skin tone (blue or pink undertones) and blue or green eyes, a cooler brown with hints of grey might be more flattering. On the other hand, if you have a warm skin tone (yellow or peach undertones) and brown or hazel eyes, a warmer, reddish-brown mascara could enhance your features better.

Remember, beauty is highly personal and subjective. What works best for you will depend on your personal preference and the look you're trying to achieve. Experiment with different shades to find the one that makes you feel the most confident and beautiful.