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