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