Generally, painting a marker even with car spray paints just wont work very well. When you paint metal the colouring just sits on top of the surface, it is VERY susceptible to chips, cracks and scratches. Think how easy cars generally mark or chip and you wouldn't dream of putting your cars body through the sort of perils a marker goes through. Also the layers of paint can adversely effect the thickness of the surface and make disassembly a pain in the arse.
Markers are coloured through a process called anodising where high currents of electricity, acid and dyes are used to bond the colour to the metal. When done well on decent materials, anodising can be extremely tough.
Slothball.com do a anodising service and their work is proper and for a fairly acceptable price.