This part will be useful for professional only who need a special rendering. There is 4 parts:
1. Color Rendering: it is possible to modify the contrast, the saturation or choose a special rendering (Landscape or Portrait). It's not really useful for astrophotographer...
2. Multi-Point Color Balance: by clicking many points, you can modify the color balance for some hues, for example the subtle tints of the visages. The global white balance isn't modified. This option is one more time destined for experts or professionals for "ordinary" photos.
3. Hue / Saturation / Lightness: personnaly, i prefer to modify those things in Photoshop, after processing is DxO. But remove a red hue in the sky can be useful. For that, choose "Reds" in the pop-up menu, then desaturate this tint to remove the red veil in the sky!
4. Tone Curve: this is the same as in Photoshop. Leave those options for Photoshop once you've had processed the file in DxO Optics.

Let's play with the color rendering.

On the right, different color rendering had been applied to the RAW file: Canon 10D, Kodachrome 64 and Velvia

On the right: RAW file developed with different color rendering.
Canon 350D + Sigma 18-50 at 18 mm open at 2.8 on a tripod. 30 s at 800 ASA.