Why can we see some gases and not others? Also why does gas have color this isn't a school question I'm just curious lol

2-bromo-2-methylbutane undergoes an e1 elimination reaction in the presence of ethanol. in the next reaction only one of the possible products is represented. although the product shown is not the major product of the reaction, notice that there is more than one way it can be produced. complete the mechanism and draw the missing substances.