We might say that someone who is exceptionally chatty can "talk a blue streak." What is the origin and meaning of this phrase? Is it generally insulting, or a nice way of saying someone is a chatterbox?
According to The Word Detective in all likelihood, the term did arise by analogy to the speed and force of a bolt of lightning, especially in “talk a blue streak,” meaning to speak rapidly and excitedly. The “blue” in “curse a blue streak” probably also invokes “blue” in the sense of “obscene.” So it it is not really insulting when you say that somebody talks a blue streak, it is just an informal way of saying that he/she talks very fast and endlessly and very often aimlessly.
To curse/swear a blue streak means to speak rapidly, too, but using swear/curse words. Cursing/swearing a blue streak is usually an outburst-- a retort or angry reaction, and short-lived. However, it can also mean using a lot of swear words repeatedly over a period of time: My teenager has been cursing a blue streak during the past month means that he/she has been using a lot of swear words, and often.
Talking or cursing a blue streak is when somebody is so wound up in something they're talking and talking and talking or cussing or cussing or cussing so hard they run clear out of breath and keep on talking and talking and talking or cussing and cussing and -- until their face starts turning blue from lack of oxygen and they just can't seem to stop until they see stars from lack of oxygen and maybe even pass clear out on the ground. Now, that's a 'blue streak'.