The Simpsons' longtime director David Silverman claimed that Smithers was always intended to be "Mr. Burns' white sycophant" and **the producers ultimately decided that it "**would be a bad idea to have a black subservient character to a rich white man," so Smithers was literally color-corrected for his next episode. The first appearance of the proper yellow Smithers with grey hair was in "There's No Disgrace Like Home", the fourth episode of The Simpsons season 1.
https://screenrant.com/simpsons-season-1-waylon-smithers-black-reason/