大惊失色

to turn pale with fright (idiom)

see 大夫[dai4 fu5]

big; large; great / older (than another person) / eldest (as in 大姐[da4 jie3]) / greatly; freely; fully / (dialect) father / (dialect) uncle (father's brother)

with great alarm

to startle / to be frightened / to be scared / alarm

to lose / to miss / to fail

to lose color / to turn pale

color / CL:種|种[zhong3] / look / appearance / sex

(coll.) color / used in 色子[shai3 zi5]