I have created a new comandos.exe file that runs the game on windows 10, no compatibility or reduced colours required and it is running smooth and no issues. Here is how I did it: 

Step 1: Rename your original Comandos application to Commandos 

You can do this by right-clicking on the game in your Steam library, selecting properties, then local files and left-clicking browse local files. Right-click on the Comandos application, select rename and make the ammendment to Commandos. 

(As some people have already posted, the spelling correction allows the game to run but not through steam) 

Step 2: Create a new Comandos application for Steam to run the game. 

Open a notepad and enter the following text on the first line (please note to adjust this for your filepath to the games installation folder): 

start "E:\Steam\steamapps\common\Commandos Behind Enemy Lines" commandos.exe 

Save this notepad as Comandos.bat 

(double-clicking this .BAT file will run the game, but Steam still cannot as it will not find the executable) 

Finally, you need to convert the .BAT file into a .exe file for Steam to see. The easiest way to do this is by using a website like http://www.f2ko.de/en/ob2e.php where you can upload your .Bat file and select 32bit Architecture 

Please note no password is required and it is best to keep the output file visible. 

Click Convert and in a few moments you will be able to download the new Comandos.exe which you need to place in your game installation folder. 

Now steam will run the game from the library with no compatibility mode or reduced colour mode required