Newb To Hobby - Question About Toning On Copper Cents

Hey all.

Last week I feel I got lucky and bought 58 rolls of pennies from an estate sale for about 10% of the price eBay sellers would charge lol. Finally cracked them open just now.

Now I'm new to coin collecting and have quite a handful of wheats. However, they are all either brown, black or a nice red color. These cents have all the above, but I'm seeing some that are blueish/purplish in color. I do apologize as the pic isn't the best, but I tried to get a lot of them in the same pic so the quality kind of lacks.

But what I'm wondering is this — are wheat pennies, or maybe pre 1982 pennies, able to tone naturally like this? Or is this artificial like from cleaning? Thanks in advance