[A. G. Maisey]

I do not know Hugh, but I believe it is highly likely that the red stones are rubies and the white stones are low quality diamonds.

The caption reads:-
selut Krawangan (open work) tretes (set with precious stones) seling (spaced with mirah) bentuk (shape) njeruk keprok (small mandarin), the word mirah means ruby, but it can also be applied to any other red stones

So taking into consideration the overall quality of this selut, my guess is that we are looking at rubies & diamonds, but these would not be high quality stones.

The stones in the selut alongside this first one uses the word "byur" which simply means "sparkling", but they look like diamonds, however, if this selut is recent work, which it probably is, they are just as likely to be cubic zirconia, which in the trade are referred to as "American Diamonds".