Formula to change font color in concatenate cell

Hi all,

Here is my question.

I would like to concatenate 3 values in one cell. The result I am looking for is the last row of the document I attached. Each value can have a different color based on the color code legend.

For those who cannot open the file, the font in the cell should look like that : 5 / 30 / 44

thanks a lot for your help!
Shawn