What does the blue arrow signify in Library?

[Blindfish]

In the library view some of the buttons to the right of the file listing are blue. What does this mean? I thought it was because I had downloaded songs to my phone but no, some are downloaded some aren't but the button is blue.

[daneren2005]

Yes the blue arrow signifies that the song is downloaded. There was an issue where some songs that were downloaded weren't having the arrow be blue in a previous version, but the version on the market should have fixed it.