I don't know what got me thinking about these yesterday - I think we were talking about associating colours with numbers and I was saying how when we were in grade 1 and 2 in school in Scotland these wooden Cuisenaire Rods were all the rage to teach little kids the basics of mathematics. The principal was that math was based on a 1cm white wooden cube - 2 of these cubes made a red 2cm long rod - 3 of them made a green 3 cm long rod etc. It was very effective way of teaching math basics to little kids(we all carried around a yellow bag of rods at school) I don't know if these still exist - but what I retained from those math lessons was not particularly mathematics it was colour association. The number 1 will always be associated with white, 2 with red, 5 with yellow, 9 with blue etc. Do you associate colours with numbers and if so how did you develop this association?