Dark Green line on shrimp?

[Makaroni]

I have noticed one of my shrimp has developed a dark green line on the top of it's body. My shrimp is also not the red variety (not sure if that helps). I'm new to keeping shrimp so I'm not really sure if this is a bad thing.

[Vorteil]

Pics would help.

[OpaeOasis]

Their digestive tract runs through their back, the color indicates that they have eaten algae