Hi Chris, I mentioned you in a previous answer which may be some use. As I said in the Q&A @ruarig (Matt Parker) and I did a power hour on accessibility and he covers emotional accessibility brilliantly. @scottkenyon may also have some thoughts.
Essentially, things that put pressure on users such as timers that cannot be stopped or extended can cause anxiety. I’m not qualified to guess at how colours affect people but I’m aware there is information on colour psychology out there. Hope that helps in some small way.