Paint only the flat part of the ceiling. The slanted part get the wall color.

Even though some of the angled parts have the knockdown ceiling texture?

I think since the ceiling has so much texture and there is really no where to change paint colors, you need to paint the flat ceiling and the slanted ceiling the same color. Everything else would be wall color.

So sorry, didn't see the knockdown from my phone. Well that is a pickle. The reasoning behind painting the slant the same as the wall is it doesn't look like the ceiling is coming down on you.

You could paint the walls and the ceiling the same color. But with the strong blue (pretty color ) it might be a bit much.

You could sand down the knockdown on the slants. That is a huge mess to do though.

You could do the walls the blue and the ceiling and slants a lighter version of the blue.

Knockdown or not I still would paint the slant the same as the wall.

Consider removing the texture on the slant in question.

I would suggest removing all the texture from the ceiling if possible.

I would love to remove all the texture in the entire house (lol) but have no idea how to do that and it’s not in the budget.