I think that the confusion for iron color comes from the color of ferric ion in water (which usually comes from ferrous ion in well water that is oxidized to ferric ion by chlorine) which is yellow* compared to that of ferric oxides-hydroxides aka "rust" which is orange-reddish though can range from yellow to red or darker red depending on the specific composition. Ferric ion is also fairly insoluble so not much of it will remain in the water -- it will tend to stain or precipitate and get caught in the filter. Unfortunately there isn't a reliable way to make it go one way vs. the other. There are some procedures that try and raise the pH, chlorine, and calcium levels by adding Cal-Hypo to the skimmer in an attempt to create more iron precipitate to get caught in the filter, but it's an iffy procedure.
Metal sequestrants can bind to ferric ion, but they bind much better to ferrous ion which is why the usual procedure is to use a reducing agent such as ascorbic acid to remove metal stains and convert ferric ion to ferrous ion. Then one adds a metal sequestrant which binds to the ferrous ion keeping it dissolved in water and preventing it from getting oxidized back to ferric ion. One needs to add more metal sequestrant over time since chlorine slowly degrades it. As for copper, it's mostly in a single state so there isn't the same need for using a reducing agent. The removal of copper stains happens more from the use of acid though such stains tend to be difficult to remove because they penetrate more deeply than iron stains.
*Technically, it is the ion complex [Fe(H2O)5(OH)]2+ that produces the yellow color (in some over-saturated high concentrations it may be yellow-brown). This complex is formed in water due to the high charge density of ferric ion (similar to how aluminum forms complexes and floc -- in fact ferric ion is often used as a coagulant just like aluminum).