To estimate the total number of different colors a human can see, we can consider that the human eye has three types of cones (red, green, and blue) that allow for color vision. Each type of cone can detect around 100 different shades of color.
If we assume that the perception of color can be combined through mixing the signals from these three types, we can calculate the total number of possible combinations:
\[ \text{Total colors} = \text{(shades for red)} \times \text{(shades for green)} \times \text{(shades for blue)} = 100 \times 100 \times 100 = 1,000,000 \]
So, the answer is 1,000,000.