The number of lights of a particular color is indicated by the number of cross marks over the color, in the line plot.
From the plot, the number of orange colored lights on the tree is 9.
[Count the orange colored cross marks.]
From the plot, there were 5 green colored lights on the tree.
[Count the number of green colored cross marks.]
The difference between the number of orange and green colored lights = 9 - 5 = 4
[Subtract the number of green lights from the number of orange lights.]
So, there are 4 more orange colored lights on the Christmas tree than the green colored lights.