24. Use red, pink, yellow, and black 4 colors to paint the 6 sides of a regular hexagon, so that the sides painted yellow and black each have one, and the sides painted red and pink each have 2. Mr. Li has some color blindness. For any two colored regular hexagons $A_{6}$ and $A_{6}^{\prime}$, if $A_{6}^{\prime}$ is obtained by changing the two sides painted red in $A_{6}$ to pink, and the two sides painted pink to red, Mr. Li, due to his color blindness, considers $A_{6}$ and $A_{6}^{\prime}$ to be the same. Find the number of distinct colorings of the hexagon under Mr. Li's identification method.
24. 15 .