feat(tutorial.css): change color scheme to match subatomic mode
feat(tutorial.css): change color scheme to match subatomic mode

cjmazey/fork_leanprover_tutorial,Hodapp87/cs6460_project,avigad/tutorial,soonhokong/lean-tutorial,Hodapp87/cs6460_project,fpvandoorn/tutorial,avigad/tutorial,Hodapp87/cs6460_project,leanprover/tutorial,soonhokong/lean-tutorial,soonhokong/lean-tutorial,fpvandoorn/tutorial,cjmazey/fork_leanprover_tutorial,avigad/tutorial,fpvandoorn/tutorial,leanprover/tutorial,leanprover/tutorial,cjmazey/fork_leanprover_tutorial