Do you design with light or paint?

After watching the above video on Steve Mould's nerdy blog and reading Ian Storm Taylor's post "Design Tip: Never Use Black" a fellow designer, Jamie K Leach and I were discussing what makes white and what makes black. She argued that black was the presence of all colors and I argued that white was the presence of all colors. That's when we realized, she thought of her colors in Photoshop as paint and I thought of my colors in Photoshop as light. Which made me wonder how other designers think of their colors in Photoshop? When you design in Photoshop or Illustrator do you imagine you're designing with light or with paint? And more importantly, how do you feel that affects your designs? If at all?

Also, here's an awesome Radio Lab episode on Colors!