3 ms·or the ink could change color based on temperature/light exposureby opportune 8y agoor the ink could change color based on temperature/light exposuregoda90 8y agoIt'd be tricky to get it just right on a sunny but cold day. You'd want it dark to absorb more sunlight, but that absorption makes it get warm despite the cold air.Moru 8y agoThe 40 cm thick snow cover would probably negate the effect.