“proud-pied April, dress'd in all his trim”
'Proud-pied' means brilliantly and variously colored: 'pied' describes a mix of two or more colors in patches (as in a piebald horse); 'proud' adds the sense of showy, magnificent display. 'Trim' means fine clothing or ornament. April is imagined as a figure strutting in a gaudy, multicolored costume.
“nor the lays of birds”
'Lays' are songs or melodic verses — here, the musical calls of birds. The word was standard poetic diction for a short lyric or melody. The speaker says that not even birdsong could move him to delight while the beloved was absent.
- TLN 1369rhetorical device
“figures of delight, / Drawn after you, you pattern of all those”
'Figures' here means copies or representations. The poet inverts the standard praise comparison: the lily and the rose are not models the beloved resembles, but copies 'drawn after' him. He is the 'pattern' — the original from which nature takes its beauty. Nature does not surpass the beloved; it merely imitates him.
historical The sonnet form “with your shadow I with these did play”
'Shadow' in Elizabethan English regularly meant a copy, image, or reflected likeness — something that resembles an original without being it. The flowers are the beloved's 'shadow': representations of him without his substance. The speaker has been amusing himself with pale imitations, not the real person.