How to use the color picker dialog to set color properties in the property editor?

This sounds like a trivial question, but it's proved quite hard to google any开发者_开发知识库thing about this.

When editing Color-typed properties through the property editor (when designing WinForms), a little editor pops up with three tabs: Custom, Web and System. I want to set a custom color by using the standard color picker dialog because none of the listed Custom colors are suitable.

I am sure that this used to be possible by double-clicking a blank color on the Custom tab, but this just picks the color being double-clicked and closes the drop-down in my VS2008. Am I imagining this, or did it really use to be possible? Can I do this in VS2008 somehow?

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Right click on a blank colour in the palette shown by the custom tab. Brings up the "Define Color" dialog (in VS2008 C# Express, and I imagine the same in other versions).

EDIT - Having discovered this by experimentation, the MSDN library describes it here.
Interestingly, no keyboard-only interface is described.