Paint mixes by taking colours away. Each pigment is a tiny filter: blue paint soaks up red light, yellow soaks up blue light. Mix blue and yellow and only green light is left to bounce back to your eye — so you see green.
Red and yellow together leave mostly red and a little green: that is orange. This is why a paint set only needs a few colours — you make the rest by mixing.
But every filter you add takes more light away. Stir all the colours together and almost no light escapes — you get mud. Every painter meets mud; the trick is to rinse and mix just two colours at a time.
Screens do the opposite — they add red, green and blue light. That is why the colours you make with paint can surprise you.
Something in the mixing dish stopped unexpectedly — the lesson continues without it. You can move on; nothing you did was wrong.