如何在饼图中制作对比色的切片？

Question

我很难以更清晰的方式显示此饼图的切片。持续的阴影很难遵循。如何使用对比色彼此相邻的切片着色？例如，S3conv会更好用红色，蓝色和黄色代替两个绿色和一个蓝色......非常感谢！

图解说明： 每个饼图代表一个实验图。 - Rot.Herb 总重量=图中所有杂草重量的总和

我用于此图表的代码是

library(ggplot2)
library(tidyr)
library(dplyr)


weedweights<-data%>%
  select(-ends_with("No"))%>%
     gather(key=species, value=speciesmass, DIGSAWt:UnknownmonocotWt)%>%
     mutate(realmass= (10*speciesmass) / samplearea.m.2.)%>%
     group_by(Rot.Herb, species)%>%
     summarize(avgrealmass=mean(realmass, na.rm=TRUE))%>%
     filter(avgrealmass != "NaN")%>%
     ungroup()

ww2 <- weedweights %>%
  group_by(Rot.Herb) %>%
  mutate(totalweedweight=sum(avgrealmass)) %>%
  ungroup()

ggplot(weedweights, aes(x=1, y=avgrealmass, fill=species, order=avgrealmass)) +
  geom_bar(position = "fill", stat="identity") +
  facet_wrap(~ Rot.Herb) + 
  coord_polar("y") +
  ggtitle("Weedbiomass by crop phase and herbicide regime")+
  theme(plot.title = element_text(size=20, face="bold", vjust=2))+
  theme(axis.text.x = element_blank(), axis.text.y = element_blank(), axis.ticks = element_blank())+
  xlab("Weed dry biomass (kg per ha)")+
  ylab("Crop phase and herbicide regime")

这是data