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