Sikhism teaches that people of every race are the same and should be treated equally:
From one clay has the Creator made countless shapes, sizes and colours. Neither are the vessels badly made or does the Creator lack any skill.Guru Granth Sahib, pages 1349-1350
At the time the Guru Granth Sahib was written (and this is still generally the case), people in Indian society were born into different castes. One word for caste was 'varna', a word originally meaning colour. People of lighter skin believed they were superior to those of darker skin. People's occupation was for many centuries determined by the caste to which they belonged. Access to education and places of worship was denied to those whose castes were considered inferior.
The Gurus taught that a person's birth-related status had no bearing on their spiritual progress. They set up langar, the practice of everyone eating the same food and sitting together. At one point a ruler came to listen to the teaching of the Gurus but left without eating with the lower caste people. The Guru issued an instruction: first eat together, then worship together. The Gurus taught that people's origins were less important than the choices they made.
Do not enquire about one's caste and birth...honour is determined by deeds.Guru Granth Sahib, page 1330