Purple is a combination of wavelengths from opposite extremes of the spectrum, which technically deosn’t make any sense, but ...

However, specific symptoms should raise our alertness—they may be visible in the eyes and hands. Although the development of a brain hematoma ... vein and sinus clots, bleeding disorders such ...

That’s right. Red and blue (or violet) wavelengths are two opposite extremes on the spectrum. When you see both of these wavelengths in the same place, you eyes and brain don’t know what to do ...