Select the test for the gamma you have estimated. The coloured blocks in each row are either the same or different. For each row, make a note of whether the blocks appear the same or different.
Gamma = 1.5
Gamma = 1.7
Gamma = 1.9
Gamma = 2.1
Check the answers. If you are missing a cone-type, you should score about 5 correct on the test for that cone-type. Otherwise you should score about 8 or 9 correct.
This test assumes that your browser can depict 24-bit colour. If this is not the case, you may need to download the GIF images to an application which can display 24-bit colour.
Selecting "Dithered Colour" on your browser may work reasonbaly well.