1 Her face so fair as flesh it seemed not,
so fair as > [was so fair that like]
2 But heavenly portrait of bright angel's hue,
portrait > image hue > appearance, form
3 Clear as the sky, without blame or blot,
Clear > Brightly shining blame > fault
4 Through goodly mixture of complexions due;
complexions due > (Due or proper combination of the four cardinal "humours" of the body whose proportions, in medieval physiology, were supposed to determine one's mental and physical qualities. Cf. 306.38:5, 310.59:3)
5 And in her cheeks the vermeil red did show
vermeil > scarlet