vertex colors are slightly lighter in editor compared to webgl builds

vertex colors, in vertex colored meshes and also in lineRenderer lines. Are lighter in editor, darker on webgl build. I'm using a very basic alpha blended vertex color shader. The shader is fine in other projects and the same meshes are fine in other projects. By 'fine' I mean, they look the same when I compare Unity Editor and webgl builds. This problem doesn't seem to affect sprites and textures, is just making the vertex colors slightly lighter (washed out) for vertex colors. I can see the same in the LineRenderer. I set the same color for start and end of the line, and the color of the line in the game window is lighter than the one I set in the LineRender options.