。
Wool dyes beautifully.
Literal
Wool [topic-は] dyeing-finish [subject-が] beautiful is.
染め上がり is a compound noun: 染める ('to dye') + 上がる ('finish up') in masu-stem form. Refers to the final dyed result. A technical term for textile work. A double-subject construction (wool topic, dye-result subject).