This is what happens when you boop the calculator snoot.

Several other Synths are being booped around this site, and Sigma is not immune to this tactile trend.

Unlike other Synths who blushes in their visor upon booping, Sigma blushes in a unique way. Due to his Vacuum Fluorescent Display, Sigma experiences a surge of electrons rushing to his face. More specifically, to the cathode lines across his display. These cathode wires normally do not emit any light, but the high amperage event results in heating of the lines to the point of becoming red-hot, resulting in an orange/red glow.

Thankfully, his cooling vents at the nose helps to keep his head cool when this happens, though it is still quite warm :3

Also a word of caution. Booping him unexpectedly may result in loss of limbs. Typical reptiles... (synthetic of course).