paint the color on a part of the histogram.

histcol.r

histcol <-function(hst, from, to, col="cornflowerblue"){
  bw<-diff(hst$breaks)[1]
  part<-c(from,to)
  xv <-seq(part[1],part[2],bw)
  yv <- hst$counts[hst$breaks[-length(hst$breaks)] %in% xv]
  for(k in 1:(length(xv)-1)){
    polygon(sort(rep(xv[k:(k+1)], 2)), c(0,rep(yv[k], 2),0), 
            col=col)
  }
}

Argument

hst: histogram object
from: specified by the x coordinate the beginning of add color range
to: specified by the x coordinate the end of add color range
col: color

Example

x<-rnorm(100)
tmp <-hist(x)
histcol(tmp,-1,1)