I want to mix some blender assets with preexisting footage but I can't get the colors to match exactly.
For example, create a new eevee scene with only a plane and a camera (no lights). Match the world surface color from an input image. Create a shadeless material for the plane, matching the emission color from the input image. Set color management to sRGB, Standard, None, Linear. Render.
Sample the output. Notice that the plane and background colors of the final render don't match the specified colors.
Note: Blender 2.80.