If you want to be pedantic about it (and I do, I'm that kinda person), it's 'blonde' with an 'e' at the end because female, because for some reason it's one of the few gendered words English still uses (I believe it's French origin?). This is of course optional, because English is fucky.
If you want to be pedantic about it (and I do, I'm that kinda person), it's 'blonde' with an 'e' at