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What is RGBA color and how to use in Microsoft Office

RGBA color codes are an extension of the RGB (Red, Green, Blue) color system which you can use in modern Microsoft Office with a little trickery. There’s an annoying difference (reversal) in settings on Office for Windows vs other Microsoft services and Office for Mac.

RGB colors have been around for a long time to describe screen colors.  It’s three numbers (0 to 255) that give the amount of Red, Green and Blue that are mixed to make a single color.  Black is 0,0,0 and full white is 255,255,255 (as proved by Sir Isaac Newton). For example RGB(128, 187, 110) makes a light green (bottom left).

The macOS color selector as used in Office for Mac

RGBA explained

RGBA adds another number which nerds like to call the ‘Alpha channel’ but us mortals can ignore that and just call it ‘transparency’ or ‘opacity’.

The fourth ‘A’ value is a number between 0 and 1.

0 (zero) is fully transparent, in other words you don’t see the color at all, just the pattern or color underneath.

1 (one) is totally on or opaque. There’s no transparency at all.  That’s the effective default when you use an RGB color only.

0.5 (half) lets half the background show through.

Wikipedia has a simple graphic showing RGBA at work over a checkerboard pattern.

At the top, the colors have full transparency (A = 0) and it gradually increases as you look down the image until it reaches opaque (A = 1) at the bottom.

Source: Wikipedia

RGBA in Microsoft Office

Office doesn’t directly support RGBA but you can fake it where Office has a transparency option, such as Text Box fill.

There’s a trap because Office for Windows handles transparency the opposite way to Office for Mac

  • Windows has a ‘Transparency’ setting where 0 (zero) means totally opaque
  • Mac talks about ‘Opacity’ and 0 (zero) means fully transparent!

The setting is totally reversed and so is the direction of the slider.

To put it another way, Office for Mac follows the A value (0 means transparent in both) while Windows has reversed it.

Why?  Who knows?  Office for Mac uses the powerful color selection tools in macOS.  Office for Windows has its own color selection dialogs.

macOS color selector as shown in Office for Mac – with opacity.
Office for Windows color selector with ‘Transparency’ setting.

But wait … there’s more confusion!

In Microsoft Designer (in previews now), there are Opacity options in two ways.

  • The color selector (left) accepts an RGBA code with an ‘Alpha’ field.
  • In some cases there’s an Opacity slider (top right)

As you can see, they work the opposite to the Transparency setting in Office for Windows.   Designer is web-based so the options are the same in either Windows or Mac.

It’s good that Designer has RGBA. A pity that the Office for Windows settings go the other way.

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