First, we split the R, G and B channels
(as I have explainds here), then sum the GREEN and BLUE channels using an ADDITION node, then using a curves node, we add contrast to the result. The result gets substracted with a SUBSTRACT node to the RED channel ( R-(G+B) ), which is blurred with the SQUEAREBLUR node (easy on that, this blur node has an horrible quality)
The ONECOLOR node is similar to the After Effect´s solid layer, simply generates a color, and with HARDCOLOR NODE, you overlay this to the generated image, and an ADDITION node overlays the result to the original image.