Russell wasn't a racist, however he was a product of his time. It was a common belief that blacks came from the curse of Ham, son of Noah. There were plenty of blacks in the Society during Russell's leadership.
Russell defended black people against racism. Russell said, [R2264] ”Without partiality (which would signify injustice): the purity and peace, gentleness, mercy and good fruits of the spirit of wisdom, lead us to be no respecters of persons, except as character shall demonstrate real value: the outward features, the natural man, the color of his skin, etc., are ignored by the spirit of the Lord, the spirit of wisdom that cometh from above. It is impartial and loves that which is pure, good, peaceable, gentle, true, wherever found and under whatever circumstances it exhibits itself.” and in R3042-3 “It is NOT true that divine favor has gone with the whites exclusively, and against the blacks and other colored races; civilizing the whites and barbarizing the others. If civilization and barbarity are to be the tests entirely, we have only to take in a wide scope of history to see the fallacy of the view presented. Eighteen centuries ago the white peoples of Europe, with their straight silky hair, were savages, idolaters, barbarians… Moreover, it was when Moses’ brother Aaron and his sister Miriam, especially the latter, upbraided him for his marriage to a negress, that the Lord defended him in the matter, and smote Miriam with the plague of leprosy as a punishment for her improper conduct and language respecting this subject. (See the account, Num. 12.) Zipporah was an Ethiopian, described in the Hebrew text as a Cushite. Ebed melech, also an Ethiopian, was one of King Zedekiah’s household, and be it noted that he was both thoughtful and zealous for the Lord’s prophet, Jeremiah, and was the commander of the thirty men who delivered him from prison (Jer. 38:7-12.) Hence the argument of those who claim that the negro is devoid of organizing intelligence or ability, except as he may have an admixture of white blood, is shown to be fallacious.”
In [R934] “…Mr. Thomson says he had seen so much of this sort of thing that he began to believe that the negro was not capable of development. But when he reached the heart of Africa, his pessimism suffered a severe shock. These are his words: “I could hardly believe I was not dreaming when I looked around me and found large, well-built cities, many of them containing 10,000 to 30,000 inhabitants. The people themselves, picturesquely and voluminously dressed, moved about with that self-possessed, sober dignity which bespeaks the man who has a proper respect for himself. I saw on all sides the signs of an industrious community, differentiated into numerous crafts—evidence sufficient to show, how far advanced they were on the road to civilization. I heard the rattle, the tinkle, and the musical clang of the workers in iron, in brass, and in copper. I could see cloth being made in one place, and dyed, or sewn into gowns or other articles of dress in other places. I n the markets crowded with eager thousands, I could see how varied were the wants of these negro people, how manifold the productions of their industry, and how keen their business instincts.”