One vertex per element, one color per generator, with an edge from x to x·s.
(1,2,4,7)(3,6,8,5)(9,10,13,18,14,15,28,19)(11,20,21,30,24,33,23,16)(12,25,26,31,27,35,29,17)(22,34,38,36,39,32,37,40)(1,3)(2,5)(4,8)(6,7)(10,15)(11,21)(12,26)(13,28)(16,20)(17,25)(23,24)(27,29)(30,33)(31,35)(32,34)(37,38) involution — undirected(1,3)(2,6)(4,8)(5,7)(9,11)(10,16)(12,22)(13,23)(14,24)(15,30)(17,34)(18,33)(19,20)(21,28)(25,40)(26,37)(27,39)(29,38)(31,32)(35,36) involution — undirected(3,8)(5,6)(9,12,14,27)(10,17,15,31)(11,22,24,39)(13,29,28,26)(16,32,30,34)(18,35,19,25)(20,36,33,40)(21,37,23,38)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.