Depending on the interview type, you can request time to set up in advance. This might not be as possible for a junior level position where they are quickly interviewing multiple candidates.
Multiple colorways are OK, if there is something special about them. As mentioned, it’s not about quantity but quality. If the multiple colorways tell a collection story, it can be OK.
Most important for a junior (I’ve interviewed a few) is to be clear what you did on the project. Did you do the upper concept? Development? Outsole tooling? I’ve had a few instances where someone brought samples I really liked, only to find out they just did the colorway, not the design or tooling and it gave the impression of dishonesty, even if it wasn’t intended.
Sketches and concepts are always good too, as long as you are able to show things that didn’t make it to production (not usually the case). Process is always good- sketches to last tape ups, to pullovers, early samples, etc. Remember you are being hired for what you CAN do, not what you HAVE done, so your thinking and process is very important.
R