What is the difference between 绿 and 青?
I am Chinese and I don't think 青色 is the same as 绿色 or 蓝色. For me, 青色 is more of a kind of blue. Personally, blue and 蓝色 also cover different shades of blue color.

This is a very common proverb:


  青,出于蓝,而胜于蓝


literally it means 青色 and comes from blue, but better than blue. Or more straightforward, 青色 is extracted from the blue plant(indigo), but is bluer than the plant. The next part is "冰，水为之，而寒于水"(ice comes from water but is colder than water). This proverb is often used to describe how students can achieve more than their teachers, or the younger ones can eventually do better. I think that is why 青 occurs in words other than color, like 青春，青涩，青年, to describe a young, inexperienced stage just like the green used in "green hand".

There is a common color name in Chinese, 靛青，which is a kind of dark blue.

check the wikipedia link about the color.
青色 is the colors like Lapis lazuli, Salvia blue, Wedgwood blue or Slate blue. The screenshot below from wiki describes the difference between 青色 and 蓝色.



For other use of "青" besides color and the implicit meaning of young， I don't know.