This webpage is being displayed on the background colour thursday.
thursday is equivalent to the colour #0000a0.
This is due to the legacy HTML parsing rules:
Add 0s to the end of the colour until its length is divisible by 3 (thursday0)
Divide the colour into three equal-length chunks (thu, rsd, ay0)
Truncate the chunks to two characters (th, rs, ay)
Replace any non-hex character with a zero (00, 00, a0)
Hence, thursday (and Thursday) are both equivalent to #0000a0.
If you don't believe me, press Ctrl+U to view the source of this page, and look at line 3.
Oh, and here's a block which is coloured in #0000a0