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)(11,13)(12,20)(14,15)(16,18)(17,22)(19,23)(21,24)(25,26)(27,28)(29,32)(30,38)(31,34)(33,39)(35,37)(36,40) involution — undirected(1,2,4,6)(3,5,8,7)(10,15)(11,18)(17,20)(19,24)(25,27,31,32)(26,28,34,29)(30,35,39,40)(33,36,38,37)(1,2)(3,5)(4,6)(7,8)(9,11)(10,16)(12,19)(13,15)(14,18)(17,23)(20,21)(22,24)(25,28,31,29)(26,32,34,27)(30,36,39,37)(33,40,38,35)(1,3,4,8)(2,5,6,7)(9,11)(10,16)(12,19)(13,15)(14,18)(17,23)(20,21)(22,24)(25,29,31,28)(26,32,34,27)(30,37,39,36)(33,40,38,35)(9,12,14,22)(10,17,15,20)(11,19,18,24)(13,21,16,23)(25,30,31,39)(26,33,34,38)(27,35,32,40)(28,36,29,37)(9,13,14,16)(10,11,15,18)(12,21,22,23)(17,19,20,24)(25,26)(27,28)(29,32)(30,33)(31,34)(35,36)(37,40)(38,39)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.