Everything after the Fall in the Garden was apparently tweaked in this sinful world--animals (And the LORD God said unto the serpent, Because thou hast done this, thou art cursed above all cattle, and above every beast of the field; upon thy belly shalt thou go, and dust shalt thou eat all the days of thy life: Gen. 3:14) Plants (Thorns also and thistles shall it bring forth to thee; and thou shalt eat the herb of the field; Gen.3:18) and Humans (Unto the woman he said, I will greatly multiply thy sorrow and thy conception; in sorrow thou shalt bring forth children; and thy desire shall be to thy husband, and he shall rule over thee. Gen.3:16).
Also, it stands to reason, He gave each creature an ability for survival in this Fallen world at that time----including the following ability in deer-----
"The golden-colored eyes of Arctic reindeer (caribou, Rangifer tarandus) turn deep blue in winter. A researcher involved with this 2001 discovery, neuroscientist Glen Jeffery.
Such unsuspected layers of complexity make the evolutionary dilemma of eye origins even more intractable, and are strong evidence for creation and design, not evolution.
It is an adaptation to optimize vision during winter twilights, when both the reindeer and their predators are most active.
Just after the sun goes down, and just before the sun comes up, is a
period called the “blue hour”.
In the blue hour, the sky has quite a
‘pure’ blue hue, i.e. very little of the other light colors present.
The blue hour is very different from the blue of the daytime sky that is
caused by Rayleigh scattering of visible light, where blue scatters
more strongly. 
The blue hour is caused by the ozone layer absorbing
almost all light but blue. This effect is dominant when the sun is just
below the horizon, so the light travels horizontally through the ozone
layer, allowing maximal absorption.
Most of the time, we don’t notice
the blue hour, because our eyes have gradually adapted to the change.
In winter, this optimization to ‘twilight ozone blue’ is particularly
important, because in polar regions, the twilight can last a third of a
day. Also, the lichen eaten by the reindeer and the wolves that try to
eat them reflect very little blue light, so appear dark against the
snow. This greater contrast, and greater ability to detect motion,
outweighs the disadvantage of lower visual sharpness." CMI
