How to heat proof aluminium windows, prevent heat from entering?
There is not a lot you can do here, to be honest, short of replacing the windows with ones better suited for your climate. Painting or covering the exterior with something of any color other than brilliant white may make things worse since shiny aluminum is reflective and is already rejecting some of the heat, and such coatings may not last.

Planting some shade trees or installing awnings to block the sun may be easier, cheaper, more effective alternatives.