System Information
Operating system: Windows-10-10.0.17134 64 Bits
Graphics card: GeForce GTX 1080 Ti/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 431.60

Blender Version
Broken: version: 2.80 (sub 75), branch: master, commit date: 2019-07-29 14:47, hash: rBf6cb5f54494e
Worked: (optional)

Short description of error
[Please fill out a short description of the error here]

sculpt mode: on objects imported in FBX (character) with Modifier Armature and a series of Shape Key , the masking works but is invisible.

Exact steps for others to reproduce the error
[Please describe the exact steps needed to reproduce the issue]

_import fbx character with outfits from Character Creator or DAZ studio. switch to sculpt mode on a garment, paint a mask ... the show / hide mask function does not work, it is invisible.
However, the mask exists and is functional.

[Based on the default startup or an attached .blend file (as simple as possible)]