I'm designing an IDE. I'm creating an icon to represent a function (which has at least one output parameter) and a procedure (which has no output parameters).

I'm undecided about using the same icon and color for the function/ procedure or use the same icon, but slightly different colors for the function/ procedure.

My question is, are there general guidelines for when to use different colors? When should different colors be used?

  • Think of the colorblind people! I am red-green colorblind, and have difficulty distinguishing those colors, and it is not that uncommon. Find someone to test your colors on. Oct 7, 2012 at 20:21
  • What is the significance for the end user (i.e. a developer) in differentiating between functions and procedures? When will the user need to make that differentiation and to what purpose? The answers to those questions will guide your design. Oct 7, 2012 at 21:37

2 Answers 2


There are two main things to consider when it comes to colors and usability: colorblind users and color psychology.

Colorblindness refers to the difficulty in distinguishing colors from each other. It comes in many forms, and affects approximately 7-10% of the male population (much, much lower for women). UX Matters has a wonderful post about the different types of colorblindness, how they affect people, and things you can do to make your interface more usable for those affected. ColourLovers also has an excellent link about different ways you can provide feedback/information to the colorblind without taking anything away from the sighted in terms of color.

When it comes to color meanings, there are a ton of references and ideas about the impact of color on the viewer. It's somewhat of a hot/open topic in Psychology. Many studies have shown significant impact; many have failed to do so. It probably won't make a huge difference to your interface, but it's always something to take into consideration.

In your specific case, using a different color could speed up comprehension/understanding when creating and reviewing, but the effect would need to be learned by the user - there aren't any well-established patterns for color in that case (i.e. unlike red->stop/green->go). You might want to look to Quartz Composer for inspiration (different colors for input/output/generic patches)


Icons need to be 'read' while colors are like words themselves: since they have a single message, they're recognized as such.

Sure, a few percent of males are colorblind (it's much more rare with females), but it usually doesn't mean they see in black-and-white, rather, they're unable to differentiate between blue and red.

  • It's not just blue and red, but otherwise your point is valid.
    – ChrisF
    Oct 8, 2012 at 9:04
  • It depends, but in general it's not like a dog's vision (which is actually black-and-white). Usually most people see yellow and brown to some degree.
    – Aadaam
    Oct 8, 2012 at 12:02

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