Note that the package munsell doesn’t work with uneven chroma values. Therefore, I changed all plots with chroma values of three to values of four. This was only five plots in total.
grid$munsell[grid$munsell == "10YR 7/3"] <- "10YR 7/4" #One plot in site 3 (AA50)
grid$munsell[grid$munsell == "7.5YR 6/3"] <- "7.5YR 6/4" #Two plots in site 1 (C40, K10) and two plots in site 2 (N0, N20)
Uneven chroma were recoded as the closest even colour