df <- data.frame(var1 = c(2,  4,  9,  3,  1,  6,  5, 10,  8,  7),
                 var2 = c(1,  4,  7, 10,  9,  2,  8,  3,  5,  6),
                 var3 = c(rep("a", 5), rep("b", 5)),
                 var4 = letters[1:10])

ggplot(data = df, aes(x=var1, y=var2,
                      shape = var3,
                      color = var3)) + geom_point(size=4)