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