Given a transparent PNG displaying a simple shape in white, is it possible to somehow change the color of this through CSS? Some kind of overlay or what not?
You can use filters with -webkit-filter and filter:
Filters are relatively new to browsers but supported in over 90% of browsers according to the following CanIUse table: https://caniuse.com/#feat=css-filters
You can change an image to grayscale, sepia and lot more (look at the example).
So you can now change the color of a PNG file with filters.
body {
background-color:#03030a;
min-width: 800px;
min-height: 400px
}
img {
width:20%;
float:left;
margin:0;
}
/*Filter styles*/
.saturate { filter: saturate(3); }
.grayscale { filter: grayscale(100%); }
.contrast { filter: contrast(160%); }
.brightness { filter: brightness(0.25); }
.blur { filter: blur(3px); }
.invert { filter: invert(100%); }
.sepia { filter: sepia(100%); }
.huerotate { filter: hue-rotate(180deg); }
.rss.opacity { filter: opacity(50%); }<!--- img src http://upload.wikimedia.org/wikipedia/commons/thumb/e/ec/Mona_Lisa%2C_by_Leonardo_da_Vinci%2C_from_C2RMF_retouched.jpg/500px-Mona_Lisa%2C_by_Leonardo_da_Vinci%2C_from_C2RMF_retouched.jpg -->
<img alt="Mona Lisa" src="https://images.pexels.com/photos/40997/mona-lisa-leonardo-da-vinci-la-gioconda-oil-painting-40997.jpeg?auto=compress&cs=tinysrgb&dpr=3&h=750&w=1260" title="original">
<img alt="Mona Lisa" src="https://images.pexels.com/photos/40997/mona-lisa-leonardo-da-vinci-la-gioconda-oil-painting-40997.jpeg?auto=compress&cs=tinysrgb&dpr=3&h=750&w=1260" title="saturate" class="saturate">
<img alt="Mona Lisa" src="https://images.pexels.com/photos/40997/mona-lisa-leonardo-da-vinci-la-gioconda-oil-painting-40997.jpeg?auto=compress&cs=tinysrgb&dpr=3&h=750&w=1260" title="grayscale" class="grayscale">
<img alt="Mona Lisa" src="https://images.pexels.com/photos/40997/mona-lisa-leonardo-da-vinci-la-gioconda-oil-painting-40997.jpeg?auto=compress&cs=tinysrgb&dpr=3&h=750&w=1260" title="contrast" class="contrast">
<img alt="Mona Lisa" src="https://images.pexels.com/photos/40997/mona-lisa-leonardo-da-vinci-la-gioconda-oil-painting-40997.jpeg?auto=compress&cs=tinysrgb&dpr=3&h=750&w=1260" title="brightness" class="brightness">
<img alt="Mona Lisa" src="https://images.pexels.com/photos/40997/mona-lisa-leonardo-da-vinci-la-gioconda-oil-painting-40997.jpeg?auto=compress&cs=tinysrgb&dpr=3&h=750&w=1260" title="blur" class="blur">
<img alt="Mona Lisa" src="https://images.pexels.com/photos/40997/mona-lisa-leonardo-da-vinci-la-gioconda-oil-painting-40997.jpeg?auto=compress&cs=tinysrgb&dpr=3&h=750&w=1260" title="invert" class="invert">
<img alt="Mona Lisa" src="https://images.pexels.com/photos/40997/mona-lisa-leonardo-da-vinci-la-gioconda-oil-painting-40997.jpeg?auto=compress&cs=tinysrgb&dpr=3&h=750&w=1260" title="sepia" class="sepia">
<img alt="Mona Lisa" src="https://images.pexels.com/photos/40997/mona-lisa-leonardo-da-vinci-la-gioconda-oil-painting-40997.jpeg?auto=compress&cs=tinysrgb&dpr=3&h=750&w=1260" title="huerotate" class="huerotate">
<img alt="Mona Lisa" src="https://images.pexels.com/photos/40997/mona-lisa-leonardo-da-vinci-la-gioconda-oil-painting-40997.jpeg?auto=compress&cs=tinysrgb&dpr=3&h=750&w=1260" title="opacity" class="rss opacity">