10-bit color is something that falls under the HDR sphere of viewing. In order to take advantage of it, you will first need to have a TV that supports it and then needs to disable it from the Xbox Series X display menu.
You might wonder why all of these things are not turned on by default. Well, it comes down to the capacity of the HDMI port that both the TV and Xbox have. You may want to turn on every new feature such as 4k resolution and 120fps and set it to the highest value but if this exceeds the data transfer rate of HDMI 2.1, which is what the Series X uses, it will result in a black screen.
If the HDMI of the TV is lower than 2.1, the black screen due to insufficient bandwidth of the TV port, or just a cheap cable could also be a problem for you.
Enabling 10bit Color Depth on the Xbox Series X
Leaving the potential issues aside, for this, I will assume that you are using a high-speed HDMI cable and your TV is capable of receiving everything the Xbox Series X can output.
Navigate to Settings->General->TV & Display Settings. In this menu, you will see an option called “Video fidelity & overscan”. Click into this and you will see there is a menu that looks like the image below.