If you need more colour correction or grading than FCPX or plugins will handle, the best way to go is out to Resolve. Blackmagic Design's grading program has come a long way since its acquisition and it continues to grow. Alexis Van Hurkman can show you more.
Blackmagic have a habit of buying companies who make great but expensive products and then re-launching them to the mass market at a fraction of the cost. That's also true for DaVinci Resolve priced at $995 for the full version, but remember that the 1080 lite version is still free to download and use without restrictions.
DaVinci Resolve is a pro application and if you want professional looking results then money spent on video training will be well worthwhile.
Ripple Training have launched their DaVinci Resolve 9 Core Training hosted by professional colorist Alexis van Hurkman. The training costs $89.99 for the 1080p, $79.99 for the 720p version and $99.99 if you would like either versions supplied on a memory stick.
"Grading describes the process of adjusting the color, contrast, and overall look of a film or video as part of the finishing process. It is during this stage that a colorist works his or her magic to create visual continuity throughout each scene, fixes or adjusts lighting and quality issues encountered during the shoot, and shapes the overall look and mood of a film by adding visual style. DaVinci Resolve 9 sets a new standard for color grading and digital mastering, and is used on many of the most popular feature films, television shows, commercials, music videos, and documentaries you watch every day."
Alexis wrote the Color Correction Handbook, a reference publication that would make a great Christmas present for, erhem, yourself! The left hand book icon is the book and the right is the Kindle version. We will suggest to Steve at Ripple that they should do a package deal for the book and the training!
Ripple Training have posted some examples online of their DaVinci Resolve training course from Alexis so that you can see the quality of lessons you will be following.
Tracking a Shape
Real-World Primary Grade Workflows
Working with Camera RAW
Creating a False Skin Tone Look
Grade Management - Linked Clips
Using Power Windows