Its obviously red, provided that it is a perfect sphere, if you pulled the red string tight enough then course it will touch all the way around, duh! the blue string couldnt be correct no matter how tight it was pulled if it were done the same as the picture, as both ends of the blue one are miles up in the air, so it cant touch all the way around with the ends up in the air.
And yes, i did vote for the blue one by accident because i have a hangover!
Uhmmm i don't hop on the bandwagon, i just thought about what would hapen if i would walk around the earth with a string in my hand, well i came to the conclusion it will never magically float when i come back to the other end of the string...