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