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