This Blender add-on creates a new panel in the side bar (n-panels?) where you can manage colour attributes as if they were layered with blending options.
Grab the zip from releases (see right-side) and install like any other Blender add-on.
Use [+] / [-] buttons to add or remove new layers. This will create or remove an associated colour attribute. Use the Sync Color Attributes button if you created colour attributes via the objects data properties panel and want them added as layers. Keep in mind though that if you were to remove that layer the colour attribute would be removed too.
The sync button will also rename the colour attributes to have the same name as the layers, except when there are layers with duplicate names in which case the layer will be renamed.
The up/down arrow buttons can be used to move layers. This does not affect the position of the actual attribute in the list of attributes.
The Blend options (per layer, with selected layer’s values being displayed) determines what values are used in the MixRGB Node of the material. The 0 to 1 value is the factor and drop-down includes all the values you would find in the MixRGB node’s properties.
A new material called Material (Vertex Paint Layers) will be added to the object. This material is used for previewing the mixed layers when Viewport Shading: Material Preview is on. 
You can switch to 
Viewport Shading: Solid to view the colour of an individual layer while in Vertex Paint mode.
Use the Unlit and Shaded buttons to change what the final preview material looks like. They are basically the same except that the Shaded version has a Principled BSDF node added before the output.
