There've been quite a few questions about raw files recently, so I've written [msg=4214]this sticky forum note[/msg] about it.
Among the things that you could try are..
[*]Using the embedded JPG instead of the raw data; it should always look good (and load faster).
[*]Trying a different color temperature / white balance setting in the options of your plug-in.
[*]If they're from a new camera model, use the DCRAW plugin and manually update the dcraw and dcraw64 executables to the latest version, as explained in the note above.
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