Default chart colors Keynote showroom
I had a look at the internals of a fresh Showroom layout Keynote file (it's a zipped folder actually). Inside, there is a index.apxl file which contains lots of data .. also color data. I wrote this short Ruby script to make a quick-and-dirty html file with all colors used in the Keynote document:

#!/usr/bin/env ruby

puts "&lt;!DOCTYPE html&gt;&lt;html lang=\"en-us\"&gt;&lt;body&gt;"
file = IO.read("index.apxl") # slurp apxl file

# iterate through file and convert color info to 8-bit integer:
file.scan(/sfa:[rgb]=\"(\d\.?\d*)\"\s+sfa:[rgb]=\"(\d\.?\d*)\"\s+sfa:[rgb]=\"(\d\.?\d*)\"/) do |w|

  r = (w[0].to_f*255).to_i
  g = (w[1].to_f*255).to_i
  b = (w[2].to_f*255).to_i
  puts "&lt;div style=\"width:100px;height:100px;float:left;background:rgb(#{r}, #{g}, #{b});\"&gt;&amp;nbsp;&lt;/div&gt;"
end

puts "&lt;/body&gt;&lt;/html&gt;" # close html


After pruning duplicate lines, this is the visual result of the process. 



These colors are used in the default Showroom layout. You can now select (one click) the individual same-colored areas of a bar graph (here: grey or red).

In the graphics inspector () you can change the colors according to your wishes. Pick the colors from above graphic with the color picker like this: