I believe that Purple was the OEM race color for KTM before going orange..
as you the 620/609cc vs the 640/625cc, try these links:
Difference between LC4 620 and 640 motors?
http://www.advrider.com/forums/showthread.php?t=214835
Up-to-date: KTM 640 LC4 Adventure changes between model years
http://www.bmwgs.com/forums/showthread.php?t=184956
They helped me..