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