The Economic Times

Home-canned red beets can suddenly turn pale, then regain their darker color days later; heat temporarily changes the pigments before the reaction reverses

Canning your own beets at home might surprise you with unexpected color changes, like a lighter hue that sometimes shows up after canning. This happens due to betanin, a pigment that doesn't tolerate heat very well. The good news is that if you store the jars correctly, this pale color can often return to a rich red over time.