I missed the llama thing but the dress thing is the fact that this picture of a dress:
http://swiked.tumblr.com/post/112073818575/guys-please-help-me-is-this-dress-white-and
Is an optical illusion and people think it’s either gold and white (as i do) or black and blue (as BlackwoolHoliday does) based on whether their visual system is predisposed to disregarding warm or cool colours as ambient lighting effects.
Ashton McAllan
Kyle Mahan
Aaron Parecki