There is nothing racist about confusing two people for each other based on them having the same skin tone. A two year old child might do it. This should be enough proof for anyone that the cause is not racism but the brain's pattern recognition system failing.
Accusing someone of racism used to be a serious charge. Now its used by many against anyone who makes any misstep where race is involved. This is diluting the charge the point of meaninglessness which provides cover for actual racism. It also repels people who see through it.
If someone mistakes two blonde people for each other, no reasonable person accuses that person of being bigoted against blondes on that basis. Their brain simply lumped those two people together using an inaccurate heuristic.
A black person without much exposure to asians might have trouble telling asians apart. A white person without much exposure to black people might make the same mistake.
In neither case is there even a hint of racism. Ignorance is not racism. It's perfectly okay not to have exposure to people of any race. Not living in a "melting pot" does not make someone a bad person.
It's also perfectly okay to have a brain that isn't great at distinguishing between people. This is just how human brains are and is nothing to be ashamed of. It is not grounds for guilt. And it's not grounds to accuse anyone of something as serious as racism.