I used the Preview Color Tool a lot in Leopard, mainly for picking color from an image. For reason unknown Apple has removed the Color Tool menu from Preview.app in Snow Leopard. Since the Annotations Tool also uses the color we can still show the Colors Pane, here’s how:

1. If the Annotations Toolbar is hidden, show it by View → Show Annotations Toolbar (shortcut: command-shift-A).
2. Click Arrow (or Oval or Rectangle) to toggle on an annotation tool and enable the Color Menu icon.

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1. Click the Color Menu icon to bring the Colors Pane up to front.
2. Now do whatever you want to in the Colors Pane.