green is overall just a pleasing color, that's why they use it for car dashes. it's cheaper and more effecient, blue's farther down the color spectrum and harder to produce, anyone who builds computers cases knows they're more expensive than a regular green or amber led. i'm almost sure if blue was everywhere people would say green was cooler, it's just the whole breaking away and looking different idea that makes blue seem cooler. blue light also scatters, so it's not quite as effective. if you have those keychain lights, they're usually red because the light "cuts" through better and you can see it since through, the blue light is naturally dimmer. my friend replaced the red light on his keychain for a blue one because he thought it looked cool, we all laughed at him when it was 50% dimmer and practically useless.