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