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