1981 Lincoln W/ Very Odd "Color"

thanks. any idea what might cause the "yellowness", on this one?

True- technically, the cents from the 1960s-1982 were a type of brass since the tin was omitted but they were not yellow brass which has a higher zinc content. Prior to the 1960s, all "copper" small cents and Two Cents were bronze- 95% Cu, 5% Zn/Sn. The brass plated Zincolns are supposed to be different because they are plated with yellow brass which gives them a distinctive color. If the zinc content of the plating was low, the color would be almost indistinguishable from a normal "red" copper plated cent.

As for your coin dbrablec, it is just a toning transition/mellowing from red to brown. I have seen that shade on a number of Lincolns, typically ones that have been lightly handled. With extensive circulation, the coins just go straight to the standard brown color.