I'm a big yellow fan lbb. Red is quite mild but I find green ones quite bitter.
I have a very easy pasta/pizza base tomato sauce recipe for babies/toddlers;
gently fry red onion and garlic, add tin of tomatos, little squirt of tom puree, splash of balsamic vinegar, sprinkle of mixed herbs. simmer and blend.
I add courgette, mushrooms, leeks, peppers, carrots, aubergine, butternut squash - anything I have in the fridge to get more veg into it.
If you want to get some protein in I sometimes chuck in a handful of red lentils (add a bit of water to it if you do).