NvEnc API - Colors are changed in encode / decode

I’m using NvEncoderCuda to encode images to h264. After decoding the result (using FFMPEG) I get the images with much more saturated colors. I could not find much documentation about NvEncoderInitParam so I don’t know if the change is controllable. Any idea how to avoid color changes with NvEncoderCuda? Any documentation about the NvEncoderInitParam? Thanks.