light the blue touch paper

light the blue touch paper

or

light the touch paper

BRITISH
If someone lights the blue touch paper or lights the touch paper, they do or say something which causes people to react in an angry or violent way. This kind of remark is guaranteed to light the blue touch paper with some Labour politicians. Tension between them had been building up for weeks. All it took was Mason to light the touch paper and stand back. Note: The touch paper on a firework is a small piece of dark blue paper attached to one end. When it is lit, it burns slowly until it sets off the firework.
See also: blue, light, paper, touch