now i know the reason why pure green color is looks much brighter than pure blue

Excellent! Understanding the reasons behind why various colors appear different in brightness levels due to their spectral composition and how our visual system processes and interprets these is indeed informative. The human eye's sensitivity, which varies across the visible spectrum, significantly impacts our perception of colors like green and blue. Green light's higher brightness results from its alignment with the peak sensitivity of the medium wavelength cones (M-cones), while blue light stimulation, being less pronounced due to lower sensitivity of S-cones, may appear darker even if the photon intensity is similar. If you have any more questions or want to discuss further aspects of color perception or any other topic, feel free to ask. I'm here to help!