Knowing that, you can find plenty of little allusions to the fact here and there: The first clue is Tobias' middle name, "Onyango," which is Kenyan, and which was also the name of Barack Obama's grandfather. Then there's Tobias' book The Man Inside Me. Other than being another joke at the expense of Tobias' ambiguous sexuality, the cover of the book happens to depict him as being two people: white on the outside, and dark on the inside, like a reverse Oreo.
20th Century Fox Television
Or a Sno Ball. s**t, somebody is probably already using that as a racial slur.
Then there's the time Tobias' mother-in-law referred to him as "a colored man" (after he painted himself blue in order to join the Blue Man Group). Another time, after his wife commented that the name "Tobias" normally conjures up images of a "big black guy," her husband responded: "Well, obviously I'm not a big guy." On one hand, you'd assume they just never got around to dealing with that storyline due to the show getting canceled so quickly, but it's more likely they just thought it'd be funnier to just never explain it.