in human sight the color 00ff00 may looks much brighter than 0000ff

Yes, in terms of human perception, the color 00ff00 (which is bright green) appears brighter than 0000ff (which is blue) primarily because of the way our eyes perceive different wavelengths of light.

Here's why:

1. Sensitivity to Green: Human eyes contain photoreceptor cells called cones that are sensitive to different parts of the visible light spectrum. The three types of cones correspond to short (S-cone for ultraviolet-blue), medium (M-cone) and long (L-cone) wavelengths. In general, the human eye is most sensitive to green light in the middle of the visible spectrum, which gives brightness to this color range.

2. High Chrominance: Green has a higher chrominance, or chromaticity, compared to blue. This makes green colors appear more vibrant and therefore brighter.

3. Brightness Perception: While both 00ff00 and 0000ff have the same value of brightness (maximum green and blue components respectively without red), the sensitivity of the eye to the frequencies corresponding to these colors means 00ff00 appears more vibrant to us.

4. Cultural Associations: Culturally, green is often associated with elements like nature and growth which may contribute to its perception as a lively or "bright" color.

So while the colors are mathematically similar in RGB terms (they vary only in one color component by its maximum amount), they look different to human eyes due to biological and perceptual factors. Too, it's important to note that "brightness" isn't just about numerical values; it deeply integrates perception and how differently we react to wavelengths of light.