Color manage your textures
There are a couple of options to ensure textures are processed in the correct color space.
The best option is to export your textures from your painting DCC as ACEScg and import them into Unreal Engine.
However, if you have existing textures in sRGB, you can convert them directly on the Texture UAsset by using the "Color Space" setting found in the Advanced > Source Color Settings section of the Texture Details panel of that texture.
In addition, above the "Color Space" option, there is the "Encoding Override" option which exposes even more options. In most cases, you should not need to change the Encoding Override when dealing with most ACES working color spaces. When set, the texture is re-encoded into the proper color space for use in Unreal.
A couple of new parameters have been added to textures in the Texture > Advanced > Source Color Settings section that allow you to control both the color space and override the encoding of individual textures:
Encoding Override - Source encoding of the texture, exposing more options other than just sRGB
Color Space - Source color space of the texture
A common scenario is changing the project wide Working Color Space from sRGB/Rec.709 (engine default) to ACEScg. If by chance some assets have been already published in the project prior to the change, you can now update the textures that were originally painted in sRGB right in the engine.
In the case of sRGB/Rec.709 to ACEScg, you would change the Color Space in the texture's Source Color Settings to "sRGB/Rec.709" to flag to the engine that the texture was originally painted in sRGB. The engine will do the work of converting it to properly view in the ACEScg working color space.
Importing ACEScg (linear) Textures
It is common to work in an ACEScg working color space in an engine - which is linear. When importing ACEScg textures (or any linear textures), use “HDR Compressed (RGB, BC6H, DX11) Compression Settings”. This will preserve the linear color lookup and full bit depth of the texture.