Evolution of human colour vision lights, which appear to be clear. Other colour perception issues include having trouble distinguishing yellows from reds and violet, lavender and purple from blue. In other cases, objects that reflect both red and blue light may appear to just be blue to these individuals. Deuteranopes, who are missing medium wavelength sensitive cones, are similar to protanopes in that they cannot distinguish between colours in the green-yellow-red part of the electromagnetic spectrum. However, deuteranopes do not suffer from dimming issues. For example, purple colors are not seen as being opposite to other colours in the spectrum but instead appear to be
Ischnura erratica have blue bands dorsally, segments 3 to 6 have narrow yellow rings and there is a large blue dorsal patch stretching from segments 7 or 8 to segment 10. The tip of segment 10 is extended into an upward-pointing forked tail. The female has two colour phases. One is similar to the male but with duller eyes and greenish-blue replacing blue. The other has pale patches on the head, a greenish thorax, and a black abdomen with narrow green rings at the base of some segments. Immature females have dull orange patches on head and thorax. "Ischnura erratica" is native