If you want to include the colours, Milieu, while I quite like the monochrome idea of Schradinger, actually, that whole concept is nice. If you like the colours, it'd be a pretty simple step to go from monchromatic to giving each magical presence a shade of colour. 

If I'm reading things rightly, the haze of magic is kind of like a mist/light/sensation, however Atlas would be sensing it. And mist and light can be quite colourful. It'd probably be a more subtle thing, and kind of an only out of the corner of his eye(or at the edge of his awareness, fleeting and gone if he focuses on it). So it could make perfect sense to sneak colour in that way, and have him slowly working his way towards learning how to 'see' the colours and understand them, from what started out as monochromatic.