Plenty of nutritional studies have shown that Continental breeds, such as Simmental, Charolais, Maine-Anjou, etc., have copper requirements as much as 50% higher than Angus and other British breeds. A quick internet search will bring up lots of documentation.
CuSO4 is the most economical source of copper - the chelated copper products, copper lysine/copper proteinates, etc., are more rapidly effective - I'd use them in stressed calves - but quite a bit more expensive. Copper oxide is a really poor source - depending upon whose numbers you use, absorption and bioavailability of CuO is from 0 to 15%, whereas almost 100% of CuSO4 in a ration or mineral mix is bioavailable.
Washed out/sunburnt color may (or may not) be an indicator of copper deficiency. Only real good way to confirm it is to measure it from liver biopsy or liver samples collected at slaughter/necropsy. Blood copper levels will remain normal until liver stores of Cu are depleted. If blood levels are low, the animal has pretty well depleted the supply stored in the liver.
TXBred was right about Iron interfering with Copper absorptionl; those red 'trace mineral' salt blocks can actually make copper deficiency worse, because they have so much Iron oxide incorporated as a filler/coloring agent.
Different forages have different capabilities to take up and present copper to the animals consuming them. Orchardgrass has higher Cu content than tall fescue - but OG is about the last thing my cows will eat, when they're grazing.
