Learn English – Word for someone who loves bright colours

From merriam-webster.com:
mouse potato (noun) slang
: a person who spends a great deal of time using a computer

The terms I've heard used to describe the gap between abs are cut and groove. You might, for example, be striving for deeply cut or well-grooved abs.

Here are two random examples that use these terms. From bodybuilding.com:

We all strive for those etched in stone abs with deep cuts that you could wash clothes on. Get great ab building information right here.

From a bodybuilding guide on streetdirectory.com:

This approach of size enlargement will help you increase groove depth in between each pack once you have already been in fat burning workout routine.

A general term for a deep narrow line is furrow:

Noun:
1. A trench cut in the soil, as when plowed in order to plant a crop.
Don't walk across that deep furrow in the field.
2. A deep wrinkle in the skin of the face, especially on someone's forehead.
When she was tired, a deep furrow appeared on her forehead.

Verb:
1. To make (a) groove, a cut(s) in (the ground etc.).
Cart wheels can furrow roads.