he can get a promotion but he can't change race. obviously option 2.
Not everything is defined by race.
it certainly defines more of someone's identity than some ephemeral economic position.
Not really, as the workers are definitely more likely to have the same sort of life experiences (with some obvious exceptions, such as the white worker being less likely to be stopped by police for being in the 'wrong neighborhood' or being shot to death during a routine traffic stop) than are two people of the same race but a different class position. A white employer is never going to experience the kind of economic privation that either worker in question is. He or she is never going to have to worry about putting food on the table, putting a child through school, or not having health insurance. Discounting all of that, and instead arguing that the white worker and the white boss have more in common with one another than the white worker and the black worker is discounting the possibility of the latter two to come together and effectively mitigate their exploitation by the boss.
Historical experience shows us that workers of different racial and ethnic backgrounds can come together and do come together precisely because of their shared experience as workers. The CIO was built on that very basis and probably did more to advance the black struggle for freedom in this country than any other institution. And, in the early part of the 1970s, working class communities were again coming together, regardless of the color line, to challenge the bosses. They lost, and as a result we got neoliberalism and the politics of identity and difference. Race is not something that exists between classes, it's something that exists within classes. The white worker and the black worker live in segregated communities and have different lived experiences precisely because the bosses (of all races and of all genders; women CEOs and black CEOs are just as much class enemies as white CEOs) because the bosses have a vital interest in keeping them apart - because the last time they came together, they caused enough of a ruckus to precipitate four decades of neoliberal assault.