Hi eraka!
Actually, this is not possible to set different colors to points in the same rows/axes directly by API, so if you want to achieve this you have to use some custom JS code. I have prepared two demos for you because you can do it in different ways. The first demo relies on a callback function called on a load of the chart, just loop through all series and all points and set colors. The second demo is changing the prototype of one core function in Highcharts - if you want to use it, just copy-paste the IIFE function to your project, but if you have multiple charts on your page all charts will be affected by this function.
Demo with forEach: https://jsfiddle.net/BlackLabel/bx7fa8zv/
Demo with changing prototype: https://jsfiddle.net/BlackLabel/vtr7bm0p/
Let me know if that was what you were looking for.
Kind regards!