Dun is to gray-beige, as stanza is to

ballad
elegy
sonnet
verse

Dun and Gray-beige are quite similar colors,  

Analyzing the meaning of stanza and the four options that are given

Dun is to gray-beige, as stanza is to verse

Stanza is a group of sentences forming a verse more specifically a group of 4 lines

Ballad is a complete poem telling a story in stanzas

Elegy is a sad poem that expresses sorrow and is normally inspired by a dead person

Sonnet is a poem made with 14 lines that not necessarily works with stanzas

Verse is a group of four stanzas.

“asleep in his bed” is personified.