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