8 、Using 2 colors to color 4 small squares on a $2 \times 2$ chessboard, there are. $\qquad$ different coloring schemes.
【Analysis】If the rotation of the chessboard is not considered, there are $2^{4}=16$ ways.
If the rotation of the chessboard is considered, then using one color has 2 ways; using one color for 1 and the other for 3 has 2 ways; using two colors with 2 each has 2 ways; in total, there are 6 ways.