labels in scale_color_manual() are ignored

[MLopez-Ibanez]

Reported first here: Scale_color_manual() labels not working

# insert reprex here
p <- ggplot(mtcars, aes(mpg, wt)) +
  geom_point(aes(colour = factor(cyl)))
cols <- c("8" = "red", "4" = "blue", "6" = "darkgreen", "10" = "orange")
p <-    
 p + scale_colour_manual(
  values = cols,
  breaks = c("4", "6", "8"),
  labels = c("four", "six", "eight")
)

The examples provided by plotly.com show the problem here: https://plotly.com/ggplot2/Scales/scale_manual/