Just want to clarify: you are asking about the colour and the shape of the sign used to mark the ballot?
I cannot vouch for the intuitiveness but I can comment on cultural appropriateness.
Colour: red/green by analogy with traffic lights. Actually the use of red may be an artefact from the days when public education materials to support elections sported the red X (at least they did/do in Canada)
Sign: x or check -- in other jurisdictions it is the tradition to mark ballots with an "X". When counting paper ballots any sign that clearly indicated a choice and didn't spoil the ballot was/is valid.
Elections Canada makes use of the X in the design of its informative WWW site
http://www.elections.ca
For an example ballot see
http://www.elections.ca/content_youth.asp?section=yth&dir=res/stu/gui&document=res_stu_guide_8&lang=e&textonly=false
...you see, its obvious, had you chosen George W. Bush, a green check would have been displayed.
Posted by Linda and Charlie at November 4, 2004 08:30 AMWell, when Manhattan's four votes for Bush came in, now I can say I know two of them!
;-)