The Subject-Mediated Remote Testing Apparatus (SMARTA) was built to train and test ruffed lemur color vision at The Duke Lemur Center in Durham, North Carolina, USA (Vagell, et al. 2019). You can see the lemurs in action in the YouTube video below.
We whistle train the lemurs to touch a red square and reinforce them with a food reward. Once they learned to associate the red square with a food reward, we gave them a two-choice discrimination task. They are either shown red and gray or red and green. They always have to choose red if they want a food reward. Because red squares will always give a food reward, red-green colorblind lemurs will inconsistently choose the red square because they cannot tell red and green apart.