One vertex per element, one color per generator, with an edge from x to x·s.
(2,3)(5,6,8,7)(9,10)(11,15)(12,16)(13,26)(14,27)(17,23)(18,24)(19,22)(20,28)(21,38)(25,34)(29,35)(30,36)(31,39)(32,37)(33,40)(1,2,4,3)(5,7,8,6)(10,15)(16,28)(17,29)(18,30)(19,27)(26,38)(31,33)(32,34)(1,3,4,2)(10,16)(12,23)(13,24)(14,22)(15,28)(17,18)(19,34)(20,35)(21,36)(25,40)(26,31)(27,32)(29,30)(33,38)(37,39)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.