Issue #191 August 11, 2009

PowerPoint Tip: Confirming your colors have enough contrast

Recently I commented on a blog post regarding colors that are used on slides. The writer had made some suggestions on colors to use or avoid based on the color wheel used by graphics professionals. While this is a good first level approach, we have all seen slides that are unreadable due to the choice of colors. I don’t have a design background, and I am guessing you are probably like me. How can we make sure that the colors we choose will be seen easily? The most important factor in making slides readable from a color perspective is not whether you choose a light or dark background. It is whether the colors you choose have enough contrast with each other. You can choose a white background and if you use light pink letters, your audience won’t see the text. Similarly, you can choose a navy blue background and if you use dark green text, it’s as good as not even there. In many workshops, people often point out that they can’t select the background color because their organization mandates a certain template or look. This is not a problem. Contrast is still important and the choice of color for text or shapes is still within your control. So how can you be certain that the colors you choose will work? Don’t rely on looking at them on your computer screen. Laptop and flat screen monitors are far brighter than projectors and give you a distorted perception of how much contrast two colors have. Instead, be sure by using the international standard tests for color contrast. A number of years ago, the World Wide Web Consortium (W3C) created a standard that tests the contrast between two colors. They developed it to help web developers create easily readable web sites. We can use these two tests to make our slides readable. Both tests are calculations that use the Red, Green and Blue (RGB) attributes of the two colors to determine if there is enough difference between the two colors. I’ve made this easy for presenters by creating an online Color Contrast Calculator that allows you to test the difference between two colors you are considering for your slides. Just go to to use this tool. The page also contains detailed instructions on how to find the RGB attributes of a color and some ideas on what you can do to improve the contrast of two colors if they don’t pass the tests. You can also use this tool as an objective viewpoint when discussing color choice with colleagues. Now you can make sure that when you are choosing colors for text, shapes, callouts or graph elements, your audience will be able to see them easily.