refactor(README): improve a bit the documentation about color depth

not sure this explain it better. I first thought that was a
multiplication (which was a bit misleading)

README.md

@@ -103,7 +103,7 @@ For instance, look at the picture down below. The first face is fully colored. T
 
 We can see that the **red color** will be the one that **contributes more** (the brightest parts in the second face) to the final color while the **blue color** contribution can be mostly **only seen in Mario's eyes** (last face) and part of his clothes, see how **all planes contribute less** (darkest parts) to the **Mario's mustache**.
 
-And each color intensity requires a certain amount of bits, this quantity is known as **bit depth**. Let's say we spend **8 bits** (accepting values from 0 to 255) per color (plane), therefore we have a **color depth** of **24 (8 * 3) bits** and we can also infer that we could use 2 to the power of 24 different colors.
+And each color intensity requires a certain amount of bits, this quantity is known as **bit depth**. Let's say we spend **8 bits** (accepting values from 0 to 255) per color (plane), therefore we have a **color depth** of **24 bits** (8 bits * 3 planes R/G/B), and we can also infer that we could use 2 to the power of 24 different colors.
 
 > **It's great** to learn [how an image is captured from the world to the bits](http://www.cambridgeincolour.com/tutorials/camera-sensors.htm).