The sudden explosion left everyone pale with fright.
Tips
history
Traced to 《汉书·霍光传》: when Huo Guang proposed deposing the emperor, 群臣皆惊愕失色，莫敢发言 - 'the assembled officials all turned pale with shock and none dared speak.' The four-character form crystallized from 惊愕失色.
memory
Image: shock so sharp the blood drains from your face. 大惊 = 'great shock' + 失色 = 'lose [facial] color.' Matches the English 'turned white as a sheet' almost exactly.
