white night - ночь без сна 
• He was hardly able to work after a few white nights. 
 
look blue - иметь унылый вид 
• Do you know why he looks blue? 
 
to sail under false colours - обманывать, лицемерить 
• Although he assured us of his support but he actually sailed under false colours. 
 
once in a blue moon - очень редко 
• Once in a blue moon we decided to go on vacation abroad but his leave was cancelled. 
 
out of the blue - совершенно неожиданно, как гром среди ясного неба 
• He lost his job out of the blue. 
 
to look through blue glasses - смотреть мрачно, пессимистически 
• Her mother looked through blue glasses at her career. 
 
green hand - новичок, неопытный человек 
• It is not a job to be handled by a green hand. 
 
catch (someone) red-handed - поймать (кого-то) с поличным 
• The children were caught red-handed in the garden trying to steal apples. 
 
white elephant - бесполезное приобретение 
• The new bookkeeping program was a white elephant and nobody wanted to us.