How many stories have we read where the main characters have blue or green eyes?  But then...what shade of blue or green?  Deep blue like cobalt or light blue like arctic ice?  Green eyes like the deepest forest or green like pears?

Contact lens charts or doll eye charts can help you quickly put a name to the color you want to use.  

I don't know about you, but I've been with people and sometimes when the sun hits their eyes just right their eyes sparkle and remind me of gemstones.

Describing what the eyes are doing

If eyes are the window to the soul, what do they reveal?  If a character is staring blankly at someone is it because 1-they're bored 2-they're annoyed 3-they've killed someone ten times in their head 4-they're thinking about that gallon of ice cream back home 5-they're thinking what a dumbass the person speaking to them is?  

Some authors just don't add any information before or after to let us know the mindset of the character.  This article was brief and pretty helpful.

https://writersinthestorm.wordpress.com/2014/05/19/eyes-windows-into-a-characters-soul/

Combined with hair and skin, this gives a more complete picture of your character.  This probably seems unnecessary but I read four works by the same author and I swear it was like the same characters were recycled in their stories.  It only takes a minute or two when you have reference charts to really flesh out a character's physical descriptions.  Don't be a slacker.