1. types: `<color>`: `rgb()` (rgb color model)

2. types: `<color>`: `rgb()` (rgb color model): alpha parameter

3. types: `<color>`: `rgb()` (rgb color model): float values in parameters

4. types: `<color>`: `rgb()` (rgb color model): mix `<percentage>` and `<number>` in parameters

5. types: `<color>`: `rgb()` (rgb color model): relative rgb colors

6. types: `<color>`: `rgb()` (rgb color model): space-separated rgb() parameters