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I will assume that the word "different" is applicable UNIFORMLY to all and each pairs/pair, literally as the condition says it.
Thus each pair is considered as DISTINGUISHABLE and individual.
Then the way to solve the problem is THIS:
First find the number of ALL POSSIBLE selections of 3 pairs
and then subtract all the selections NOT CONTAINING any black pair.
Solution
1. The number of all possible selections of 3 pairs (disregarding the color) is
20*19*18 = 6840.
2. Without 8 black pairs, there are 20-8 = 12 other pairs,
and the number of selections of 3 pairs among these 12 pairs is
12*11*10 = 1320.
3. Thus the number under the question is the difference 6840 - 1320 = 5520.
Answer. There are 5520 selections satisfying to the problem's requirements.