Effect 'Solid Color' was broken in 5.1.0. it shows output all white when option 'show image' in enabled.
... previewing in certain condition also makes output go full White.
Layer 1 - Layer Router - Effect Solid Color + Mirror
Layer 1 - Layer Router - Effect Solid Color
Layer 2 - Clip 1 (opacity 100%)
Layer 3 - Clip 2 (opacity 0%)
Now click to preview Clip 1 - Output goes All White
As soon I raise the Clip 2 Opacity the White disappear
Maybe ppl should wait until this release is stable and not rush into live like last time