Why compounds shows colours in flame test ?

Metal (M) shows crimson red colour in flame test and its halide is deliquescent then metal (M) could be :

Which one of the following gives red colour in flame test?

What types of elements give colouration in flame test and why?

Which of the following cations does not import colour to the flame in flame test ?

A solid (S) is a compound of group 1 element and gives violet colour in the flame test. (S) is:

The pair of metals which do not impart colour in flame test is