In terms of button sets, you almost always need a red button to signify that this button does something dangerous (or perhaps just irreversible). And it must be done without making the user read, so usually bright red is needed. And if you have multiple shades of red (even an orange, brown-ish orange, or purple are pushing it I think) for different buttons, it becomes confusing and defeats the whole purpose.

Just taking into account the need for one red (and only one red), I'd probably rule out half of these as unusable combinations in an actual web app.

The other half look great though! ;-)