Hello fellows…
I dont know what key i tap, but now my model is in greyscale… Someone know what i did? Sry for my noobism! =P
Check the Render palette. You should be in Preview render, but it looks like you might be in a different mode.
i think its because youre using flat color as a material, change it to basic material and see if it gets normal.
Letus is right. I missed that in the screen shot. 
Good catch!