Googlorider's favicon.iso looks different

The post is not so hot about anything, so I write to my personal blog.
I noticed a strange thing:
At work (Win NT, Firefox 2.0.0.4) The Google Mobile icon is monochrome.
At home (Ubuntu 7.10, Firefox 2.0.0.11), the icon has recently become colored:

I understand that I myself am a fool and all that, but why did she still become colored? The account is the same. The address of the icon is also the same: www.google.com/reader/ui/favicon.ico .
Explain to me, wise habracheloveki, please.

UPD: Yes, today (the next day), the icon has become colored :)