I added color with writing over some of the areas with a gold (I thought gel) pen.
Then I used a white gel pen to highlight other areas.
As I was doing more bags, the gold pen started releasing a more intense gold ink, similar to a gold leafing pen. So I went back and redid the earlier bags with another gold pen I had (the first one started to get blotchy). I think this more intense gold adds more interest to the overall design.
I'll reveal what I placed in these bags the day after Christmas.