Re: [manifest] Add icons_background_color instead of background_color (#387)

@benfrancis `theme_color` is used to color parts of the UI, which is different from just coloring in the background on which an icon sits. For example, Pinterest uses white for their MS live tile:

```HTML
<meta name="msapplication-TileColor" content="#ffffff">  
```
But their theme color is a darkish red: 
```HTML
<meta name="theme-color" content="#bd081c"> 
```

It wouldn't make sense, IMO, for them to sit their logo on a red background - because it would get lost as it's already red with a thin white outline. It also wouldn't make sense to use #fffff at the `theme_color`, because their brand color is "#bd081c". 

In short: It's better to have specific control over each design element - rather than forcing one to serve the purpose of another.  

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Reply to this email directly or view it on GitHub:
https://github.com/w3c/manifest/pull/387#issuecomment-119070738