Different caps, different materials etc, but same effect.
The original kit came with two 'green' 0.047uF caps (marked as 473 on the cap). Running them combined in series, as in the diagram, would give you an effective value of ~0.023uF. A single 0.047uF cap gives a darker tone.
Green or brown cap doesn't matter (up to a point) just have a close look at them and see if they are marked as 473(letter) or 223(letter). 473 is 0.047uF, 223 is 0.022uF. If you want a darker tone use a single 0.047uF cap (or two 0.022's in parallel). If you want a less dark tone like an LP, use a single 0.022uF (or like diagram two 0.047's in series).
Make sense?