Answer by Zoe for Creating orthomosaic from *.las point cloud in R

Okay, so I figured out how to do it, although it's not very elegant:

# load datapoints <- readLAS(input_path)# returns the RGB values for the highest pointsRGBZ <- function(r,g,b,z) {  bands = list(    R = r[which.max(z)],    G = g[which.max(z)],    B = b[which.max(z)]  )  return(bands)}# create & save orthoortho <- grid_metrics(points, ~RGBZ(R,G,B,Z), res = 0.1)writeRaster(ortho, output_path)