# File lib/rubygame/color/models/base.rb, line 55
        def over(other)
                c1, c2 = self.to_rgba_ary, other.to_rgba_ary
                a1, a2 = c1[3], c2[3]

                rgba = [0,1,2].collect do |i| 
                        clamp( a1*c1.at(i) + a2*c2.at(i)*(1-a1) )
                end
                
                rgba << ( a1 + a2*(1-a1) )
                
                wrap( rgba )
        end