I thought your question was clear. You can clean and brighten the spokes with steel wool or an SOS pad, or even sandpaper. It'll be a pain at the crosses and near the hub, but it can be done. bare steel is darker than plated steel (sort of a dark battleship gray), and without the plating will rust anew fairly quickly. You can prevent that to an extent with sprays like LPS-1 or WD-40, but you'll have to keep after it, and it'll be a dust magnet.

Whether you clean them up or not the strength will be compromised to an amount dependent on the depth of the rust. In most cases it won't be dangerous, since spokes aren't likely to fail en mass. But if you do get breakage you won't have a choice about rebuilding or replacing the wheels.