rely on R's subsetting

Hey, I think you should do it this way. Right now I have to [a] look up first how many colours are in each palette (extra step), and [b] I cannot take just eg colours 2:4.

You might say -- ok, do wes.palette(5, 'Darjeeling2')[2:5]. Fine. But in this case why have the call to `n` in the first place?