Succinct way to set multiple factor levels of different variables to same color in ggplot scatterplots

Question

Consider the following simplified dataframe:

x =  c(.35, .35, .37, .5, .55, .56, .9, .91, .89)
y = c(.35, .36, .35, .22, .27, .25, .88, .9, .87)
clu3 = as.fac