my favourite North Borneo stamps

Just love the detail and the colour. Part of the 1911 high values set. The middle $5 has an unlisted lighter brighter shade more similar to the shade on the 1925 set. Could it have been a colour trial?
The $10 stamp on the extreme right is actually from the 1925 set and is perf 12 rather 14. I do not possess a 1911 $10 stamp as yet.