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