Green’s Dictionary of Slang

vanilla n.

[for ety. see vanilla adj.]

1. (US black, also vanilla malt) a white person, esp. a female.

[US]J. Smiley Hash House Lingo 6: The entrance of a good looking woman is heralded with vanilla.
[US](con. 1930s–50s) D. Wells Night People 118: Vanilla malt. A white girl.
[US](con. 1940s) C. Bram Hold Tight (1990) 158: All our people, honey. And all flavors [...] But mostly vanilla.

2. (US gay) non-penetrative sex: cuddling and mutual masturbation.

[US]R. Scott Rebecca’s Dict. of Queer Sl. 🌐 vanilla — non-leather or non-kinky sex or the people who have that kind of sex.