It's funny because our own web application (which we have been using), we implemented colors in a similar way. The color was green if student mark=max mark, red if student mark=0, and orange otherwise (e.g. there was a penalization due to wrong letter-cases or spaces). However, with our tool this wasn't a problem for us because we had a public and a private switch.
There is no problem, it's okay. The course starts in September, and we will be using the plugin as such. Maybe in the future we can propose a patch. :)
The regent wants to use 1 for each public test, 24 for each private test with a penalization of 10.
The problem with using Pre-check is that we want to penalize wrong submissions. We want them to be proficient in programming and debugging the program in the computer first, and think twice before insert it in Moodle and "checking" the code.
We will also explore combinator-template grading. Thank you!