Here above you see three images (click to enlarge). These are all three examples of natural anodized aluminium. The left-most image is an example of a plain, natural anodized louver. This is also known as standard anodizing.
The other two images show combinations of untreated natural anodizing (left) and pre-treated natural anodizing (right). These pre-treatments are, from left to right, brushing and polishing. Brushing roughens up the surface. Polishing makes aluminium even more reflective than when it is just natural anodized.
Brushing or polishing is also possible in combination with the colours below.
The above colours are an indication. A colour also appears differently on a screen than on aluminum. Powder coating in a RAL colour is also possible.