Since tone mapping has changed (from ACES to Khronos neutral), it is
normal that colors changed... You can restore the ACES tone mapping from the new options in the Advanced -> Rendering -> Deferred rendering menu.
Be aware that depending whether the EE setting in force is a PBR-aware one or a legacy one (and depending whether or not "Adjust HDR for legacy" is on or not for the latter), and also depending on the "Exposure" mode (auto, 150% 100%, 50% etc), you will get variable results.
However, this is not a bug, unlike the CAS shader bug.