r - Add color to text in geom_text based on condition -

i making plot pvalues plotted text using geom_text. pvalues given in file pvaluesmir21combined.

i want add red colour text (fdr) if value < 5e-02. idea how can done?

ggplot(tumornormalmir21_5p.m3, aes(x2,value)) +    geom_dotplot(aes(fill=variable),binaxis = "y") + coord_flip() +   theme_bw(base_size=8) +   theme(axis.text.y=element_text(hjust = 0)) +   geom_text(aes(x, y, label=fdr, group=null),data=pvaluesmir21combined,size=2)   > pvaluesmir21combined             fdr  x  y 1  p = 8.3e-02  1 13 2  p = 6.3e-05  2 13 3  p = 3.2e-17  3 13 4  p = 4.8e-22  4 13 5  p = 3.1e-10  5 13 6  p = 6.7e-11  6 13 7  p = 3.2e-24  7 13 8  p = 2.1e-06  8 13 9  p = 1.9e-02  9 13 10 p = 9.4e-06 10 13 11 p = 1.5e-03 11 13 

you can try function scale_color_manual

ggplot(tumornormalmir21_5p.m3, aes(x2,value)) +   geom_dotplot(aes(fill=variable),binaxis = "y") + coord_flip() +  theme_bw(base_size=8) +  theme(axis.text.y=element_text(hjust = 0)) +  geom_text(aes(x, y, label=fdr, group=null, color = ifelse(as.numeric(sub("p = ", "", fdr)) < 5e-02, 0, 1),data=pvaluesmir21combined,size=2) +   scale_color_manuel(values = c("red", "black")) 

see link http://docs.ggplot2.org/0.9.3.1/scale_manual.html