Windows users link to download VideoLan x264 codec.
Adobe solutions regarding CS4.
Adobe suggest using a YUV codec (such as a DV or v210 codec).
Tip: Use a high-quality, lossless Quicktime codec like Animation or PNG to render a comp.
Then use a the Adobe Media Converter to compress to H.264 mpeg.
This is the MeGUI for x264.
As part of the install it includes AVISynth.
It might require you to download missing codec.
This has its own learning curve.
For now I am simply rendering to Targas, re-importing to After Effects, then rendering to QuickTime 100% PNG. The files are large but not as huge as Animation files.
The colors are great.
Another x264 GUI is StaxRip
Yet another free GUI for x264 and FFMpeg is FFCoder.