how to change name of legend variables in ggplot code example

Example 1: how to change labels on legend ggplot

scale_color_manual(values = c("#D16103", "#4E84C4"),
                     labels = c("Justin", "Myself"))

Example 2: labs fill ggplot2

df <- data.frame(x=1:10,group=c(rep("a",5),rep("b",5)))

legend_title <- "OMG My Title"

ggplot(df, aes(x=x, fill=group)) + geom_density(alpha=.3) +   
    scale_fill_manual(legend_title,values=c("orange","red"))