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