How can I create raster plots with the same colour scale in R

Easy solution now is to use the zlim option.

plot( d, col=rev( rainbow( 99, start=0,end=1 ) ),zlim=c(0,1) )

Added as an answer in response to @Tomas

The answer I ended up using is:

plot( d, col=rev( rainbow( 99, start=0,end=1 ) ), 
    breaks=seq(min(minValue( d )),max(maxValue(d)),length.out=100) ) 

Since the image::raster function specifies that the image::base arguments can be passed (and suggests that image::base is probably used), wouldn't you just specify the same col= and breaks= arguments to all calls to image::raster? You do need to get the breaks and the col arguments "in sync". The number of colors needs to be one less than the number of breaks. The example below is based on the classic volcano data and the second version shows how a range of values can be excluded from an image:

 x <- 10*(1:nrow(volcano))
 y <- 10*(1:ncol(volcano))
 image(x, y, volcano, col = terrain.colors( length(seq(90, 200, by = 5))-1), axes = FALSE, breaks= seq(90, 200, by = 5) )
 axis(1, at = seq(100, 800, by = 100))
 axis(2, at = seq(100, 600, by = 100))
 box()
 title(main = "Maunga Whau Volcano", font.main = 4)



 x <- 10*(1:nrow(volcano))
 y <- 10*(1:ncol(volcano))
 image(x, y, volcano, col = terrain.colors( length(seq(150, 200, by = 5))-1), axes = FALSE, breaks= seq(150, 200, by = 5) )
 axis(1, at = seq(100, 800, by = 100))
 axis(2, at = seq(100, 600, by = 100))
 box()
 title(main = "Maunga Whau Volcano Restricted to elevations above 150", font.main = 4)

A specific example would aid this effort.