I don't want to hurt any ones feelings so I would usually lie. Like in high school my friend always had horrible weaves like the full head ones with black, shiny, plastic bss hair and on the first day she'd have it in of course I would look, so if i looked and said nothing she would know that I think it looks terrible, so I would just say "oh, your hair looks nice".
Recently my friend shaved her hair and dyed it bronze and i was imagining something terrible and was not looking forward to seeing her at uni because I'd have to lie but luckily it actually looked good. I told her "you know i was dreading seeing it because I thought I would have to lie and say it looks good but it looks great" and she said that she would want me to be honest because she wouldn't want to walk around looking terrible...it's just not in me to be brutally honest.