6  Custom colours for groups

custom_fill_scale <- scale_fill_manual(name = "",
                                       values = c("Men" = "red",
                                                  "Women"= "blue"))

shape_plot(my_results,
           col.x        = "risk_factor",
           xlims        = c(15, 30),
           ylims        = c(0.75, 2),
           exponentiate = TRUE,
           xlab         = "BMI (kg/m\u00B2)",
           ylab         = "Hazard Ratio (95% CI)",
           col.group    = "group",
           ciunder      = TRUE,
           add          = list(scale.fill = custom_fill_scale))

custom_colour_scale <- scale_colour_manual(name = "",
                                           values = c("Men" = "red",
                                                      "Women"= "blue"),
                                           guide = "none")
shape_plot(my_results,
           col.x        = "risk_factor",
           xlims        = c(15, 30),
           ylims        = c(0.75, 2),
           exponentiate = TRUE,
           xlab         = "BMI (kg/m\u00B2)",
           ylab         = "Hazard Ratio (95% CI)",
           col.group    = "group",
           ciunder      = TRUE,
           colour       = "group",
           lines        = "lm",
           addaes       = list(lines = "colour = group"),
           add          = list(scale.fill = custom_fill_scale,
                               scale.colour = custom_colour_scale))