Color coding is inaccurate for past releases
The color coding in the Ubuntu 12.04 specific view is inaccurate. This is because the values for the First seen and Last seen columns do not change to release-specific values. This means that you will often see the rows become greyed out when you select Ubuntu 12.04, because the Last seen version is from Quantal.
Fixing this will either require inserting release-specific First seen and Last seen values into the BucketMetadata Column Family, prefixed with a high ascii character to reduce the number of seeks (read the bucket metadata common to all releases, seek, read the release-specific metadata), or will need a new Column Family, which comes with its own set of performance penalties around locating multiple rows (rows are partitioned randomly across the Cassandra cluster).
Alternatively, we could look up the row in BucketVersions and map each found version to a lookup for the Ubuntu releases in which it is published. This is costly as it involves talking to Launchpad.