R: ggplot better gradient color

Question

I am using ggplot to plot Proportional Stacked Bar plot. And the Plot I am getting is something like this:

Answer 1

Thanks @zelite and @SimonO101 for your help. This is simpler version of what both of you proposed. Adding here for the completeness.

library(ggplot2)
library(reshape2)
library(RColorBrewer)

getColors<-function(n){
   mypal<-colorRampPalette(brewer.pal(12, "Paired"))
   sample(mypal(n), n, replace=FALSE)
}

PropBarPlot<-function(df, mytitle=""){
   melteddf<-melt(df, id=names(df)[1], na.rm=T)
   n<-length(levels(factor(melteddf$variable)))

   ggplot(melteddf, aes_string(x=names(df)[1], y="value", fill="variable")) + 
      geom_bar(position="fill") + 
      scale_fill_manual(values=getColors(n)) + 
      theme(axis.text.x = element_text(angle=90, vjust=1)) + 
      labs(title=mytitle)
}

df <- data.frame(id=letters[1:3],
             val0=1:3,
             val1=4:6,
             val2=7:9, 
             val3=2:4, 
             val4=1:3, 
             val5=4:6, 
             val6=10:12, 
             val7=12:14)

print(PropBarPlot(df))

Thanks.