Uhh...in Photoshop Elements 2.0, it's CTRL+U, but I dunno whether they kept it for newer versions or other language packs.
http://img209.imageshack.us/img209/9444/testdg7.jpg
In CS2, you have to follow Image > Adjustment > Hue/Saturation.
http://img209.imageshack.us/img209/139/test2yz8.jpg
Or, again, use CTRL+U
BTW, your request is available in the Anime Signature Request thread:
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425x153px
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405x153px
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385x153px
Don't touch the 425x153px version - it's the original, full-length sig, but I didn't trim its size to below the 50kb limit. The 405 et 385px versions, however, are forum rules-friendly.