There is nothing about parakeets' color that relates to their personality. It is how they are raised and tamed that matters!
the color is rainbow or black
No, They are not naturally blind, but they can become blind if they have an accident to do with their eyes, e.g. Attacks from dogs and cats, car clips, or any injuries done to their eyes.
yes
Ultraviolet spectrum
yes and no one of my green parakeets killed one ather and if you only have one bird its friendlyer
Yes. They are color blind. :)
Depending on your Parakeets color, it's perfectly normal for parakeets to not have blue on it's head...
All dogs are color blind
it depends on which color blind test u fail.but id call it part color blind
No, pygmy goats are not color blind.
In short, yes. The key is can those two specific blue parakeets get along. Color doesn't matter, but the two parakeets personalities may clash. If you have had a parakeet for a long time, he may not take kindly to an intruder. Often if you have three, two will bond and pick on the outsider. It is really about the individual birds not the color.