2，3，4，5，6，7，8，9， 10
In the worst case, a card in the middle of a set of two cards is separated, such as:
2,3 | 5,6 | 8,9 | j, Q|A or 2 | 4,5 | 7,8 8| 10/0, J|K, a, etc.
According to the pigeon hole principle, if you touch 10 cards, there must be 3 adjacent points. Then arrange the four colors into a matrix:
2, 3, 4, 5, 6, 7, 8, 9, 10, j, q, k, a red.
2, 3, 4, 5, 6, 7, 8, 9, 10, j, q, k, a black.
2, 3, 4, 5, 6, 7, 8, 9, 10, j, q, k, a grass
2, 3, 4, 5, 6, 7, 8, 9, 10, j, q, k and a
According to the simplified segmentation method, it is obtained that 4 1 sheet is needed, and there must be 3 adjacent points regardless of the color.
If we turn this problem into a mathematical classification, I believe there are more mathematical solutions to this problem.