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