Dead people don't do much science. So mars colonists will need to first focus on being self sufficient. The colony will need geologists and industrial chemists that can find raw materials for machinists to make into tools and products useful for the survival of the community. Here's a catalog of over 80,000 tools that a martian machinist might find useful. We need to trim this down to a working set that would allow duplication of the set and creation of any other thing they might need. Simple, reliable and relatively easy to produce should be the guideline.
Where to start? I'm going to dive into the middle and start with the Electric motor / generator. This will either use electricity to turn a shaft or the shaft can be turned to produce electricity. We need to be able to produce it's component parts: Housing, insulated wire, magnets.
Magnets are easy to make. You need a piece of iron in the right shape to become the magnet and an electromagnet to produce a magnetic field. An electromagnet is just a piece of iron with an insulated wire wrapped around it and a current run through the wire. You just need insulated wire.
To produce wire you need a metal roller to feed a rod and wire mill. It seems everyone on the internet wants to sell you enameled wire but nobody wants to tell you how to make it (I've found industrial processes but they are too great a scale for our martians) still looking... Basically you dip your wire in a liquid insulator that is cured on the wire. But I want to find a good example.
The metal parts for our motor/generator will be cast and milled. You may remember casting from shop class, you need liquid metal and a sand mold. Lathes, mills and grinders are basic machinist tools for turning hunks of metal into useful things. All of this may sound complicated but it really isn't. It's all in a days work for a person with the skills. You only need lightweight tabletop units. These can be used to produce all the parts for their bigger cousins. I part company with OSE with regard to the multimachine since I think discrete tools make a bit more sense. But I'm sure it would get used and is designed to be easily manufactured. The thing to note is the multimachine is made by someone with general mechanical skills.
Three or four colonists specializing in motor/generators should be able to produce a variety of different size motors every day. It's actually not required for survival but it's so useful to have for a variety of needs.
Perhaps simpler is the hydraulic motor. While it doesn't generate electricity it is fairly easy to make and drives a turning shaft that can give motive force to other machines and vehicles. It requires a hose to distribute power.
More fundamentally is the need to work iron and steel which is just more like the above, but that's enough about machinists; how about the chemist and electricians/electronics?
A chemist is needed because the colony is going to need more than just the simple stuff like water and oxygen. We breath out poison CO2 gas which has to be scrubbed from our environment in a simple, reliable way that doesn't break down. Beyond that are the polymer insulators needed for our wire. Beyond that is everything else. We'll need quite a few chemists who will need laboratory equipment. Which is to say, we need to include a colonist or two that is also a glass blower. Glass has other uses as well of course.
Fortunately, the advanced electronics that will be hard to produce ISRU are both small and light. They might be imported from earth for quite a while. Life support will not be based on electronics that have to be imported. That would be a really bad design. The good news is the colonist do not have to depend on advanced electronics. There's an awful lot they can do with discrete components they build themselves. We landed on the moon during the age of discreet components don't forget.
Also it should be noted that we don't have to get this all right on the first try. We are going to need to supply the missing gaps. But those gaps will be known (because current colonists will tell us) and will be the first thing we select for in new colonists.
Imagine this underground shirtsleeve working environment. Older related post.
We also shouldn't forget 3D printing. Update: $600 with case.