One of the reasons users jailbreak their iOS device is because it gives them the ability to change the font using tweaks like BytaFont.
Developer Hamza Sood who has revealed a number of hidden iOS 8 features, has posted some screenshots from his Twitter account, which reveals that iOS 8 includes configuration options in a hidden Settings panel, which could allow iPhone and iPad users to tweak the UI with different fonts and also change the text colors and highlights.
However, as developer Steve Stroughton-Smith points out it seems unlikely that Apple will provide this customization options to the end user, and could be useful to a developer to debug label and tint colors.
Developers can access these hidden customization options by enabling the UIUseAlternateUI global preference in the iOS 8 UI kit on their device.
It would be wishful thinking to expect Apple to enable these configuration options when it releases iOS 8 later this fall, but I won’t be surprised if a Cydia developer releases a jailbreak tweak to enable this hidden settings just like the SpringBoard settings in iOS 7.