I work with geologists who are trying to figure out how to use Qgis to batch apply colour values to coordinates so that we can visually see differences or patterns.
From the attached photo of soil samples I've created an Excel file containing all the sample numbers and their corresponding average RGB colour (using the Photoshop color picker). The geologist has all the samples and coordinates in Qgis but only knows how to manually apply an colour value to each sample point which will take foreverrrr.
Is there a way to do this automatically so that we can see a grid of slightly varying soil colours?
(Just as an example, and I hope this doesn't confuse the question, but it occurred to me that a pixel level view of a(ny) raster image represents essentially the same kind of effect we are looking for... except each pixel would be a real life soil sample colour, and the location would be the coordinates in Qgis where that sample/colour came from. It doesn't have to be colour-up-against-colour like my example, but hopefully that helps illustrate the idea)
edit: I have tried doing this with an expression as advised by user PolyGeo but am getting a NULL error in the expression dialog after following these steps: First we go to Layer Properties > Style Tab > Category ... then open the Expression Dialog > select Color dropdown > select color_rgb () option then input the variables into the brackets using the picker on the corresponding column labels Red, Green, and Blue. The resulting expression is color_rgb("Red", "Green", "Blue"). At the bottom of the dialog it says 'Exit Preview Error: NULL' This seems simple enough but we are clearly not doing something correctly.