I've created convex hulls for an NMDS plot but I don't know how to change their colors. How would I go about this?

#codes

phylum.dat <- read.csv("Phylum data for R.csv", stringsAsFactors = T, header = T, row.names = 1)

diversity(phylum.dat, index = "shannon")

specnumber(phylum.dat) #species number

beta <- vegdist(phylum.dat, "jaccard", binary = TRUE) #jaccard distance

mean(beta)

dist(beta) #distance matrix

NMDS <- metaMDS(beta, distance = "jaccard", k = 2)

plot(NMDS, display = "sites", type = "text") #adds labels to plot

treat=c(rep("Treatment1",4),rep("Treatment2",4),rep("Treatment3",4))

ordihull(NMDS,groups=treat,draw="polygon",col="grey90",label=F)