This card tracks a proposal that's currently part of the Community Wishlist Survey: https://meta.wikimedia.org/wiki/2015_Community_Wishlist_Survey
The Wishlist Survey voting phase lasts until Dec 14th. After the voting has concluded, the top proposals will form the backlog for the Community Tech team to investigate and address.
See also T101246: [GTWL] Epic: Highlighted wikisyntax while editing articles [AOI] and T104479: Provide a modern wikitext editor , which may overlap/duplicate.
There have been some experiments around color-coded WikiText editing (including an English Wikipedia gadget and a working implementation in the Android app). This could be made into a real feature of the WikiEditor extension.