Average changes in color over time (days since the start of each treatment) for adult azure sand grasshoppers kept on bluish-gray stones (blue symbols and lines) or reddish-brown soil (red symbols and lines). Color is expressed in the three independent dimensions of the CIE-L*a*b* space (see text). Lines show the predicted values for each CIE-L*a*b dimension according to a fitted model containing Time, Substrate, Sex, Time:Substrate and sqTime; we excluded the subject random effect for better visualization. Continuous lines and circles are for females while dashed lines and triangles are for males. The “Red Earth” treatment had to be restarted using grasshoppers from the same field location but captured later in time. As a result, the timing of data collection is out of phase between treatments, and L is initially slightly lower for “Red Earth” individuals (since the species gets darker with age).