How much red/orange is needed to stimulate hunger? A common claim thrown around is that red and orange are great for restaurants because it stimulates hunger. However, I've heard time and time again that this does not work in web design because you need a whole room to be red/orange to stimulate hunger; one such claim is here but I can never find an academic source to back this up.

How much of a color is necessary to actually provoke this reaction? Is it feasible for on-screen design to actually evoke hunger or is that a misapplication of this finding?
I tried to find a source to back up the claim that 'red' stimulates hunger. I couldn't, and in fact I found a study that suggests the exact opposite: the color red reduces food intake, because it acts like a stop signal (Genschow et al., 2012).

This also reminded me of a study by Brian Wansink and colleagues at Cornell, who had study participants consume Pringles in which every 7th chip was dyed red. They found that these people actually consumed fewer chips than controls (where none of the chips were dyed red). This may be due to the color of the chip, but another likely hypothesis is that  changing colors gave participants an implicit signal of how many chips were eaten. (i.e., if all chips were red, their intake would be the same as controls)

If red/orange does stimulate hunger, it is likely a very weak effect, and highly context-specific. Therefore, asking "how much red" might not be the appropriate question to ask.


  Genschow, O., Reutner, L., &amp; Wänke, M. (2012). The color red reduces
  snack food and soft drink intake. Appetite. LINK
  
  Geier, A., Wansink, B., &amp; Rozin, P. (2012). Red potato chips:
  Segmentation cues can substantially decrease food intake. Health
  Psychology, forthcoming. PDF