My beardie, Dar, is soooo spoiled he will only eat the white dubias. I have to scavenge the freshly molted ones for him or he won't eat. Unbelievable. He runs after them immediately and devours them the second he sees them. As for the brown dubias... He just pretends not to see them, or looks at me like, "Really? I'm not eating that!" He thinks the freshly molted white ones are soft and succulent, like vanilla pudding... Nom, nom! He has me well trained!
Try putting a small blob on calcium on the brown ones. My dragon has a thing with white objects and if he gets picky about dubia, a quick sprinkle of calcium always get him going after them. He will often leave any behind that don't have enough dust on them.
I'm so glad I saw this!. I recently started giving him the molted ones because he's not full-grown and I didn't want to give him the ones that were too hard. Now he seems to prefer them! I don't have that big of a colony yet and I'm having to dig through them to find the white ones