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