(N/A) Muscles contain a red-colored $O_{2}$-storing pigment called myoglobin.
Myoglobin content is high in some muscles,which gives them a reddish appearance; these are called red fibers.
Red fibers contain a large number of mitochondria,which utilize the stored oxygen for $ATP$ production,making them aerobic muscles (e.g.,flight muscles in $Aves$).
Conversely,some muscles possess very little myoglobin and appear pale or whitish; these are called white fibers.
White fibers have fewer mitochondria but a high amount of sarcoplasmic reticulum,and they rely on anaerobic processes for energy (e.g.,human eyeball muscles).