As a geeky spinner/weaver, I feel obliged to refine the "tow head" discussion. Flax is processed into linen thread through a wonderful collection of words. The harvested stalks are retted (rotted) in water. Then they're broken, scutched, and hackled. The short fibers left in the hackle are tow fibers. These are spun into coarser yarns of the kind used in traditional sauna towels. The remaining (very) long bast fibers are wet-spun, using a distaff, into line linen. The result is the smooth, lustrous yarn which is then woven into what most people recognize as linen cloth.

As for color: tow and flax are not naturally white-blond. Instead, they're a pale mousy-to-golden brown. The yarn or cloth gets the pale color from bleaching, traditionally done in the sun.