I used contact paper on all my tanks...you can buy rolls at Walmart or any other discounter.I had no trouble finding dark blue,dark green and black.Hardest part is getting all the bubbles out!
Why dont u just get and pot of black emoltion paint! and use a small fine decorating roller......coating light coats gradualy! till jet blackkkk. works perfect.
It would be best to avoid painting the tank as you never know how much unwanted particles or chemicals could get inside it (deadly). I recommend using the board or the tint. In case you get sick of it in the future, you can just simply remove the board or peel the tint off and change it to something else that suits your taste.