Thanks TIG for the snippets - perfect.

For others, this is the code I have so far. It has lots of room for improvement, and I'm happy for others to improve, extend, and post back here.

I assigned attributes to each face with a key/value of faceid/x.

model = Sketchup.active_model
entities = model.entities
selection = model.selection

#Define array
faces = []

# choose either the selection, or the active model
if model.selection.empty?
  #  UI.messagebox "You have nothing selected. This will color all faces that are not grouped."
  entities = model.active_entities
else
  entities = model.selection
end

#go through every entity, and if it is a face then add it to the faces array
entities.each do |e|
  faces.push e if e.is_a? Sketchup;;Face
end
#Debug; how many faces are going to be shaded
#UI.messagebox "No of faces in model/selection; " + faces.length.to_s


#get the materials from a csv file which has corresonding faceids
@filepath=UI.openpanel("Face Color Code Choose File...","","*.csv")
if not @filepath
  puts "FACE COLOR CODE FILE - CANCELED."
  @go_on = false
  Sketchup.send_action("selectSelectionTool;")
  return nil
else
  @go_on = true
end

if @go_on
  #read the file into the instance variable @alltext
  @alltext=IO.readlines(@filepath)
  #debug; how many lines/rows were in the file?
  #UI.messagebox "Number of rows in file is " + @alltext.length.to_s

  faces.each do |m|

    @currentfaceid = m.get_attribute("fn","faceid",nil)
    #UI.messagebox "@currentfaceid = " + @currentfaceid.to_s
    #UI.messagebox @face

    #now apply the material to each face
    0.upto(@alltext.length-1) do |i| #beginning with 0
      line = @alltext[i]
      if line
        line.strip! #remove whitespace
        line.chomp! #remove carriage returns
        # we'll assume csv file in the format 'faceid,material_name'
        # e.g. "...\n6,red\n7,green\n..."
        if line and @currentfaceid == line.split(",")[0] # e.g. "6"
          #Apply the material
          @matchedcolor = line.split(",")[1]
          m.material =  @matchedcolor # set material - e.g. "red"
          m.back_material =  @matchedcolor # set material - e.g. "red"
          ### you can add extra tests, make materials if not existing etc etc
          break ### we leave the do loop as we have a 'hit'.
        end
      end
    end

  end


end

The contents of the CSV file, for reference:

faceid,material
1,CadetBlue
2,Aqua
3,DarkOrange
4,LawnGreen
5,Red
6,PowderBlue
7,Yellow

Things that need improvement:

make it executable script from a menu
make it work on groups and not just faces
pass the contents of the CSV into an array once rather than reading the file over and over

and plenty of more things I'm sure!

Thanks Chris for your reply,

The attributes were created using AttributeManager like http://code.google.com/p/sketchupattributemanager/

In an ideal world, I'd have the faces colored by a range of colours derived from the spreadsheets high and low values, much like your ColorByZ script! Instead of using the z-value from the model, the script would use the spreadsheet's value for that particular faceid. Faces without a faceid would not be colored.

The ColorByValue script would have a UI with a drop down of available columns to choose from. But I'm getting ahead of myself.

I'm brand new to Ruby so it is a little daunting at first go...

I'm looking for a way to color a face based on the value of a cell in a spreadsheet (or CSV or similar).

If I have a cube with attribute faceid=1 to faceid=6, can I color the cube automatically (or from a script) that retrieves the corresponding hex color from the column "faceid" in my spreadsheet?

I've seen scripts that can export to a CSV or similar, but what about importing or linking to a spreadsheet?

Any ideas welcome,

Antony