A son asked his mother the following  question: 

 ' Mum, why  are wedding dresses white? ' The mother looks at her son and replies: 

 ' Son, this shows your friends and relatives that your bride is pure.' 
 The son thanks his Mum and goes off to double-check this with his father. 

 ' Dad why are wedding dresses white?  '  
     The father  looks at his son in surprise and says:

'Son, all household appliances come in  white.'