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