Apple Computer has switched to color screens for all its standard iPods, leaving only black and white screens on iPod minis.

“We think this continues to add heat to our lineup,” said Greg Joswiak, vice president of iPod product marketing. Joswiak declined to comment on reports that the iPod inventory had begun to swell ahead of Tuesday’s announcement, saying that the company is in a quiet period ahead of its earnings report next month.

The simplified lineup features a new 20GB color screen model for $299 (the same price as the older monochrome version), a 60GB model for $399 ($50 cheaper), and an updated iPod U2 Special Edition with a color screen for $329 ($20 cheaper). The company has dropped the 30GB iPod photo model, which sold for $349.

Apple also said that starting today iPods will offer “an easy to use Podcast menu, including bookmarking within a Podcast and the ability to display Podcast artwork in color” to coincide with the release of iTunes 4.9.

The iPods also include a podcast menu that allows users to bookmark spots within a downloaded recording and display color artwork associated with the program. Podcasts, or downloadable audio files, are offered by radio stations ranging from BBC to Clear Channel. Newsweek, ESPN and a host of amateur disc jockeys also offer the downloadable shows.

Apple said the iTunes podcast director includes more than 3,000 audio programs. The company has not said whether it plans to eventually offer paid podcasts through the service.

Unsurprisingly, all of the new full-size iPod models support the photo and album artwork features of the previous iPod photo models, allowing users to view their photo libraries on the iPod’s screen or on a TV. Apple said the new 20GB iPod holds up to 20,000 photos, compared to the 60GB version which holds up to 25,000. Both can import photos from a digital camera with the optional iPod Camera Connector.