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