ggplot：仅用于单个变量的手动颜色分配

I have this plot:

我有这个情节：

ggplot(data3, aes(year, NY.GDP.MKTP.KD.ZG, color = country)) + geom_line() + 
  xlab('Year') + ylab('GDP per capita')
  labs(title = "Annual GDP Growth rate (%)") +
  theme_bw()
ggplot(data3, aes