The phrase "more umber" refers to something that is darker in shade or has a deeper, richer tone. Synonyms for this phrase could include words like "darker," "deeper," "richer," "more saturated," or "more intense." Other possible synonyms might include "more earthy," "more brown," or "more rustic." Depending on the context in which the phrase is used, other terms like "shadowy," "moody," or "dusky" might also be appropriate. Ultimately, the choice of synonym will depend on the specific meaning and tone that the speaker or writer is trying to convey.