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