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