This is for all the character designers out there. It’s not a tool so much as an observation. If you’re designing a female protagonist be aware of the temptation to make her a redhead.
Your thought process will go something like this, “Brunette’s are so serious and I don’t want to alienate blonds. Then again, blonds invite all kinds of stereotypes. How about a redhead? If she's sassy she'll have red hair but if she's normal, like a mom, maybe just brown hair with red highlights.”
Watch almost any Western animated movie or TV show and the female lead will be a redhead or she’ll have brown hair with red highlights. Once you see the pattern you notice it everywhere and it’s weird. Supporting characters will have other hair colors but it’s likely the protagonist will have red, brown or reddish-brown hair.