Depends on what you mean by "coloured"! I've seen articles where famous anglers promote use of bright red and yellow lines, and I don't think I could bear to have them on my reel, but I'm happy enough with subdued colours.
I seem to have got the idea years ago that clear reel lines are less robust than coloured lines - but I couldn't justify the generalisation, even though I could name one or two clear lines that seemed to get more easily damaged in use.
As to spooking fish, I tended to think (or maybe not even think, just assume) that clear lines would spook fish less, as they might not be so easily seen. Then I read a convincing article that claimed fish don't spook when they can see a line - they just swim around it. They spook when they bump into lines they don't see, so you're better off with something they can! So I've no idea which is right.
More generally, even though we do get "line bites", it's odd we don't get more. Often you can fish a float shotted to a speck with the line below in the middle of a shoal of fish milling around after what you're feeding - and not see that speck move except when you have a bite. I wonder then why more fish don't bump the line and give false bites. Can they see it? You might be using a low-diameter line in coloured water, yet still line bites are rare.