This Question has been related to this one:

https://gis.stackexchange.com/questions/370986/making-colours-from-table-with-colour-percentages-rgb-codes

In that scenario I have made sure that my layer has the right colours based on a expression. This is just because this certain dataset has "standard" we all have to follow.

**The thing is this is based on a **single symbol expression** (aka the hexcode rgb). The colours are right, however when I want to construct a legend by the "ouderdom" layer, the colours of the legend are wrong.** **This is ofcourse because when I try to categorize it by that field, in the legend random colours are chosen, causing the legend to display the wrong colours.**

**So to clarify my symbology of the layers needs to based on the "ouderdom" field categorisation but the colouring needs to still happen the same expression (so no random colours), how do I do this?**