Your materials settings are terrible.
- you should switch from glossy_lossy to glossy
- in mat1 both channels are black, you might better go with a black matte material
Why do you say it's ark blue? it appears black in the preview. If it's dark blue in a render and you use a sky, this might be due to the second point above.
Jeanphi, why glossy instead of the new glossy_lossy? What are the differences? And, if glossy is better then why add glossy_lossy?