What is the difference between amber eyes and light brown eye because they look similar?

Answer 1

Amber eyes would have more yellow or gold in them and aren't very common. Light brown eyes would be, well, light brown.

Answer 2

Eye colour names are not very precise. Some people are "lumpers" they will group similar colours together with the same name, others are "splitters" they will subdivide similar colours into a number of different names.

If you are a splitter, you will divide light brown with names like amber, mocha, caramel, honey etc, etc. If you are a lumper you will call all them all light brown. (and if you are a super lumper, you will just call it brown and include the dark browns too).