I did not know that yesterday!

The rainbow appears on bumper stickers, T-shirts, computer mouse pads, and especially on flags. In 1978, a San Francisco artist named Gilbert Baker designed a rainbow flag with eight horizontal stripes. Similar to how the American flag's 50 stars stand for the 50 states and its 13 stripes represent the 13 colonies, the eight stripes on the rainbow flag were symbolic.

From top to bottom, the colours and their meanings were:


Since then, the flag has changed a bit. The current version has six stripes instead of eight. However celebrating and understanding diversity is still the underlying theme.

source: ask.yahoo.com