Finally got around to making myself a ref sheet! This is his "standard" look, but Bastian's colors change with the seasons!
Summer months: warmer fur color, salmon-y skin and internal color, and amber iris
Winter months: cooler/darker fur color, blue-ish skin and internal color, and icy blue/lavender iris
Irregularities in temperature can occasionally even cause heterochromia, which returns to normal over time.
Also important to note that his antlers can be in various stages of development depending on the time of year, and he may occasionally find himself with just one for a short time.
As for clothing/accessories, he's usually wearing a flannel, but also enjoys scarves, collars, and hanging things in his antlers.