As far as im concerned they are almost always appropriate.

At this point black suede pumps are worn with black tie!

Brown suede shoes are appropriate with suits for the office. I cant tell you how people who dont understand them will react to them but Americans in the Northeast wont even notice you have them on. For weekends, they come in a variety of shades styles and sole types. Sometimes a contrast cream stitch in the upper can lend a 1930s chic.

i would keep the shades relatively close to the coloration of the pants. In summer a medium colored brown, even with some red in it that has a look of spice (nutmeg?) is right. I had a gf who called them doberman red. In winter, often the shoe that has the color of ground espresso beans is right.

I know the Neopolitans wear those suede shoes that look like a light grey/tan artist's eraser but I cannot get used to them. They are not right for NYC but may well be perfect for strolling around Pompei.

Order them and enjoy them. Many elegant and informed people wear suede year-round.

I don't feel they are particularly appropriate at night.

I can imagine something smart in suede at a nightclub or certain restaurants of course, but you're right, not quite something for black-tie even though Gravati makes a suede opera pump.

I never understood the rules about suede. I always see them as lounge lizard lothario style. I hate those waxed and distressed looks on suede. Suede should always look smart not scruffy.