Red light plus blue light equals which color light?

• A. Magenta light
• B. White light
• C. Yellow light
• D. Green light

Answer: (A)

Mixing light uses additive color theory. When red and blue light shine together, the brain perceives a magenta color because those two wavelengths combine to form a color that isn’t present as a single spectral line. In the additive system, red plus green makes yellow, blue plus green makes cyan, and all three together produce white. So red plus blue specifically gives magenta, which is why that option is the correct choice. If you were mixing pigments instead of light, red with blue would often look purple, which shows the difference between additive (light) and subtractive (pigment) color mixing.