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