It's a reference to a well-known fanfiction called Velma, in which the writer (who was later outed as an abusive sex offender) made Velma black in order to insert herself as the nerdy girl. The fanfic was panned by critics and fans alike for completely misunderstanding everyone's characters and using offensive and even racist clichés, such as Velma selling drugs to, and I quote "white girl with too much money".
It's a reference to a well-known fanfiction called Velma, in which the writer (who was later outed as an abusive sex offender) made Velma black in order to insert herself as the nerdy girl.
Velma was made Indian. She had dark skin, but she wasn't made black. However, they did make Shaggy black.