You can build the column names with the paste0() function.
MAT <- matrix(1:20, ncol = 10)
MAT
[,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10]
[1,] 1 3 5 7 9 11 13 15 17 19
[2,] 2 4 6 8 10 12 14 16 18 20
colnames(MAT) <- paste0("rh", 0:9)
MAT
rh0 rh1 rh2 rh3 rh4 rh5 rh6 rh7 rh8 rh9
[1,] 1 3 5 7 9 11 13 15 17 19
[2,] 2 4 6 8 10 12 14 16 18 20