iOS 7.1.x comes with great options for reducing transparency for those that are harder at seeing. Unfortunately, Apple didn't have those options available in iOS 7.0.x (the pre-Pangu
era). With that being said, if you have iOS 7.0, 7.0.1, 7.0.2, 7.0.3, 7.0.4, 7.0.5, or 7.0.6
installed on your iOS device(s), then a new free jailbreak tweak called Contrast70
by iOS developer PoomSmart could be useful to you if you're harder at seeing.