Operating system: Windows-10-10.0.17763 64 Bits
Graphics card: GeForce GTX 970/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 417.35
Broken: version: 2.81 (sub 2), branch: master, commit date: 2019-08-16 18:51, hash: rBe8ffe25eb111
Short description of error
Changing vertex theme color on particle edit mode Hair will not reflect on 3D Viewport. It relfects on mesh edit mode though.
I also tried on 2.80 official build same problem. But It's fine in 2.79.
Exact steps for others to reproduce the error
01. Give default Cube hair particle system
02. Change the mode to Particle Edit mode
03. Press 2 to switch to Point
04. Open Preferences / Theme / 3D View. Find Vertex and change the color will not changing the point color
[Based on the default startup or an attached .blend file (as simple as possible)]