Why does my Ellipse mask and FastGaussian nodes have no effect on my image? I was following a video tutorial and I want to achieve the same effect in the Fast_Gaussian, I want that like sort of dark colors that form like a circle ( Vignette ), Also when I change the color or the tone the whole image just changes the color , or turns darker/lighter

my scene :


Desired result :
You need to add a RGB input to the mask.



Also, to control the darkness of the vignette, use a Bright/Contrast node to the mix.