If you’re going to be doing any reencoding, particularly for color alterations, it’s always going to be a better idea to convert it to a lossless (or near-lossless) codec first. H264 is… not that.
I thought CRF=0 was lossless for h264/x264. That’s what I’ve read everywhere on the web at least.
Technically, I believe CRF 0 is only “visually lossless”. Meaning with the naked eye you shouldn’t be able to see any difference, which is not the same as a true lossless codec like Lagarith, huffy or MagicYUV. A truly lossless codec is like using winzip or winrar - just as you can unzip or unrar to restore the original uncompressed file, you can take an uncompressed AVI, compress it with one of these codecs and then take that output file and resave it as an uncompressed AVI and the MD5/HASH will be identical to the file you started with. You won’t get that with h264 CRF 0.