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