Seems like something funky is going on with the way colors in shaders are processed. I am working with a MediaTexture, which is always forced to be Color Sampler and not Linear Color Sampler in Unreal. When I plug that in it looks fine in Unreal and darkened in Noesis. I was able to get the exact color by doing this in the shader. Now the texture looks washed out in Unreal but correct in Noesis.

This is the expected behavior. We assume that the colors returned by Materials are sRGB, not linear.