who invented the rule that the a1 square must be a dark color?

Why does Eo__________________ keep starting this type of thread.

It was the destiny...

Nobody has a clue... Because its a mistery.

Now go play some chess.

maybe chess should be played on a dark green board, with a yellow grid for the squares?

No doubt there is board out there like that somewhere.

I think it was an entirely arbitrary decision. The use of light and dark squares was purely a way to visually identify one square from another. Some people argue that a light square in the righthand corner represents the right hand of God and the "light" color of the square in question repesents good (versus evil). Since chess has it's origins outside of the Christian world, this myth is busted. Honestly, I think it was simply a choice without much thought put into it.

exactly

  This is from the 'The Oxford Companion to Chess" under Board "....    The two players sit opposite sides of the board.This is set so that each has a light-coloured corner square on the right hand side (a8 and h1) , a convention dating from medieval times and endorsed by Damino. White's Queen  stands on a light square. Black's on a dark square, the 'queen on her colour' as the beginners are told.  ...."