Understanding how and why animal secretions vary in property has important biomimetic implications as desirable properties might co-vary. Spider major ampullate (MA) silk, for instance, is a secretion earmarked for biomimetic applications, but many of its properties vary among and between species across environments. Here we tested the hypothesis that MA silk colour, protein structure, and thermal properties co-vary when protein uptake is manipulated in the spider Trichonephila plumipes. We collected silk from adult female spiders maintained on a protein fed or protein deprived diet. Based on spectrophotometric quantifications we classified half the silks as ‘bee visible’ and the other half ‘bee invisible’. Wide Angle X-ray Scattering and Differential Scanning Calorimetry were then used to assess the silk’s protein structure, and thermal properties respectively. We found that although protein structures and thermal properties varied across our treatments only the thermal properties co-varied with colour. This ultimately suggests that protein structure alone is not responsible for MA silk thermal properties, nor does it affect silk colours. We speculate that similar ecological factors act on silk colour and thermal properties, which should be uncovered to inform biomimetic programs.