Happens on master (481375fefe)
Doesn't happen on 9.x.x/release (2ddf9def91)

Repro steps:
1. Create a new shadergraph
2. Create a new Texture2D property
3. Set the Texture2D property to "none" and color to "black", "grey", or "bump"
4. Drag the texture2d out into a sample texture 2D node and drag that to the graph's "color" output
Expected result: the node preview and master preview are the correct color
Actual result: the node preview and master preview colors are white
Note: the color appears correct in the resulting material
Note 2: unlike previous similar bugs, closing and reopening the shadergraph doesn't fix this bug