When you’re as old as Altgeld Hall, you deserve a nice cleansing scrub. The stony skin of the building dates to as far back as 1896, after all, and a lot of history, and other gunk, has built up on the stone.
Even a U of I student’s thesis from more than 50 years ago notes the coloration change. Muriel Schienman (MA, '69; PhD, '81; art history), in her 1969 master’s thesis, “Altgeld Hall, The...