Lincoln Penny Colors

Well. I'm no expert but I've searched millions of cents and have a quite large collection of books on them. My best educated guess is most of it is just toning and dirt from circulation. The 1986 hasn't seen much circulation so it has still retained much of it's luster, it hard to tell from the pic but the 73 could be cleaned or maybe it has just toned a nice yellow shade. Besides the major composition changes ( bronze to zinc) most of the other coin compositions in the 40's were not different except the 1943 year which is zinc coated steal and 1944-1946 they used spent shell casings from the war melted back down so the sometimes show different colors at higher grades.

Red, red-brown, brown. Is used to describe the mint luster. Red is perfect. Red-brown is almost perfect with some of the luster fading and brown is when all the luster is gone. This can be caused by many things both environmental toning and age. You can have 2 coins both in perfect condition with no wear on them and one can be brown and the other red. The red is worth a bit more because it's still has a shine to it and eye appeal but grading wise they both show no wear so they might grade ms-red and ms brown.

The 1973 cent might be bronze. You will need an excpert to confirm that.