There was a discussion about the color gestures recently. I have an idea how to make them more usable and discoverable. The basic idea is to display a small strip with a gradient under the cursor. To understand what I mean check out any recent version of GIMP or GThumb, load up an image too big to fit in the window and see what happens when you drag on the small four-way arrow in the lower right-hand corner of the window.
Instead of a thumbnail, a color gradient corresponding to the setting that is currently being adjusted would be displayed. The feature would be activated by dragging on a small widget with a two-way arrow superimposed over a color circle or a gradient. The appearance of the icon could change depending on what is adjusted (H/S/L) but that's optional.
Why this idea is an imporvement over the current gesture functionality: First, it will be much easier to get the color you want quickly. Second, it will be more discoverable. Third, the widget could be reused to pop up similar icons on the canvas to allow the user to e.g. adjust the color of a gradient node (there would be something that enables them, maybe a separate tool, to minimize visual pollution).
I believe the "everything on canvas" paradigm is superior to "tweak values in dialogs" and one of the things Inkscape does right, so expanding on-canvas functionality seems to be a good idea to me.
Regards, Krzysztof Kosiński.