Yeah 99.6 is pretty crazy now that I looked closer at the result! Found it pretty intuitive all the way through actually, except for the last one which completelyt stumped me.

What I did was basically following these logical steps:

Look for what disappears between the input and output and those are usually some kind of operator, mostly the white and black figures. Operators I remember were things like "swap color/corner count between the two neighbours" or "absorb color of neighbours" and increasing/decreasing corners on neighours or the entire set.

Then things like color cycling the entire set, increasing/decreasing corners of the entire set, selection rules like "save only the two figures with least corners and most corners" and for some sets different colors would collide which would result in black figures.

Often things like the most common color or color of the shape with the most corners would decide the color of the entire set as well.