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