Did I tell you I just LOVE your leaves!?!
I've been doing a little zendoodle stitching too and you are right; I have found that the more contrast between the thread and the background, the better; my favorites are a couple I did for my DGD using very bright pink thread on a black background. Your idea to highlight it with the gold paint to bring out the design really worked out well here.
How did you apply the paint to the fabric? Did you use a brush similar to painting on paper or canvas, or something else? Do you need to heat-set the Lumiere paints, or are they permanent when just air-dried? I just ordered some paints from Dharma that need to be heat-set but they are Jacquard Textile Colors, not the Lumiere paints.
Did I tell you I just LOVE your leaves!?!