Diffuse is the color of an object in 3d programs including DAZ Studio 4.x. Here is the Wiki Page for Diffuse – http://docs.daz3d.com/doku.php/artzone/pub/software/dazstudio/reference/st_diffuse
You can find the Diffuse on the Surface Tab. loading most objects will load the DAZ default shader.
A discussion about the Surface Tab is incomplete unless you discuss the Lighting Model. Many objects load with the lighting model of plastic unless the author made more specific shader presets. The Lighting Model are choices in the way the render engine interprets the specularity of an objects surface. So with the previous statement you would assume it has no effect if you are only playing with the Diffuse Channel. Not so. It seems that the Skin Lighting model does effect Diffuse. See below.
The Glossiness of the Diffuse surface seems to be expanded and softened compared to the plastic lighting model. But also brightened or stronger. Glossiness is directly tied to specularity so this make me even more curious since the Specular Channel was at 0%. So I will now turn the Specular Channel up to 100% and show the effects of Glossiness.
Specular and Diffuse at 100%. Plastic Lighting Model. Spotlight 100%. At Glossiness 100% with these setting there is no specular highlight.
There are really billions of different settings and combinations of settings for the DAZ Studio 4 Surface TAB. Diffuse and Specular are the 2 most used shading channels in any product. Many times there are maps associated with the channels. Next chapter will continue with Diffuse, Glossiness, Specular and Lighting Models on the DAZ 3D Studio 4 surface tab. Happy rendering.