We know that stars have different colours because they have different energy. So blue stars have a lot of energy because the blues's frequency is very high (E = hV). The colour of the star is its electromagnetic radiation which is influenced by the elements of the star. All stars issue white light, but we know that the absorption spectrum isn't a continue spectrum because some elements absorb some radiations. So does the blue star contain elements which absorb low radiations and so there are only high radiations which color the star with blu/violet? And what are these elements? How can we know if an element absorb radiations with low or high frequency?

We know that stars have different colours because they have different energy. So blue stars have a lot of energy because the blues's frequency is very high $E = h\nu$. The colour of the star is its electromagnetic radiation which is influenced by the elements of the star. All stars issue white light, but we know that the absorption spectrum isn't a continue spectrum because some elements absorb some radiations. So does the blue star contain elements which absorb low radiations and so there are only high radiations which color the star with blu/violet? And what are these elements? How can we know if an element absorb radiations with low or high frequency?