You can mark the audios by enclosing them in HTML elements with different classes:
<span class="apple">{{Audio1}}</span>
<span class="orange">{{Audio2}}</span>
then use these classes to apply different styling for audio buttons inside them. If the images you want to use are simple monochromatic shapes, this can be done purely with CSS. For example, applying the following styling
.apple svg circle {
fill: none;
stroke: none;
}
.apple svg path {
d: path("M45.595,28.383c0-4.093,1.409-7.817,3.714-10.59-2.408-2.27-5.601-3.688-9.141-3.746-2.943-.045-5.681.829-7.946,2.354-1.534,1.03-3.554,1.03-5.088,0-2.265-1.525-5.003-2.399-7.946-2.354-7.563.12-13.564,6.461-13.636,14.024-.111,12.682,5.23,20.454,8.017,24.155,2.756,3.665,4.909,4.789,8.517,4.789,2.051,0,3.96-.62,5.543-1.686,1.235-.825,2.863-.825,4.093,0,1.587,1.066,3.491,1.686,5.547,1.686,3.607,0,5.757-1.124,8.517-4.789,1.641-2.176,4.165-5.766,5.939-10.934-3.697-2.796-6.131-7.531-6.131-12.909ZM38.424,9.435c2.616-2.761,3.999-6.178,4.109-9.435-3.246.285-6.584,1.849-9.2,4.61-2.616,2.761-3.999,6.178-4.109,9.435,3.246-.285,6.584-1.849,9.2-4.61Z");
fill: red;
}
.orange svg circle {
fill: orange;
stroke: none;
}
.orange svg path {
d: path("M32.157,6.834c-13.558,0-24.587,11.242-24.587,25.061s11.03,25.061,24.587,25.061,24.587-11.242,24.587-25.061S45.714,6.834,32.157,6.834ZM10.102,28.88c.507-3.91,2.007-7.642,4.347-10.79.314-.418.791-.679,1.308-.718h.121c.478,0,.936.192,1.274.541l9.645,9.88c.531.541.671,1.288.386,1.992-.29.703-.907,1.126-1.655,1.126h-13.64c-.521,0-1.018-.231-1.361-.629-.338-.393-.492-.89-.425-1.402ZM15.757,46.412c-.516-.034-.994-.295-1.308-.713-2.34-3.147-3.841-6.88-4.347-10.79-.068-.511.087-1.013.425-1.407.343-.398.835-.625,1.356-.625h13.645c.748,0,1.365.418,1.655,1.126.285.703.145,1.451-.386,1.992l-9.645,9.88c-.367.379-.878.575-1.394.536ZM31.192,52.677c0,.531-.227,1.038-.618,1.387-.386.344-.873.497-1.375.428-3.812-.516-7.45-2.061-10.523-4.46-.41-.325-.661-.797-.695-1.328-.034-.526.154-1.043.521-1.416l9.625-9.87c.352-.359.791-.546,1.25-.546.236,0,.473.049.709.148.695.29,1.105.925,1.105,1.687v13.971ZM31.192,25.078c0,.767-.41,1.402-1.105,1.692-.695.29-1.428.143-1.959-.403l-9.625-9.865c-.367-.374-.555-.89-.521-1.416.034-.531.285-1.003.695-1.328,3.073-2.4,6.711-3.944,10.523-4.465.082-.01.159-.015.236-.015.415,0,.815.152,1.139.443.396.354.618.856.618,1.387v13.971ZM48.44,17.372c.043,0,.082,0,.121.005.521.034.994.295,1.308.713,2.34,3.147,3.841,6.88,4.342,10.79.068.511-.082,1.008-.42,1.402-.347.398-.84.629-1.361.629h-13.635c-.753,0-1.37-.423-1.66-1.126-.285-.703-.14-1.451.386-1.992l9.645-9.88c.338-.349.796-.541,1.274-.541ZM33.122,11.112c0-.531.227-1.038.622-1.392.323-.29.724-.443,1.139-.443.077,0,.154.005.232.015,3.816.521,7.459,2.065,10.528,4.465.415.325.661.797.7,1.328.034.526-.159,1.043-.521,1.416l-9.63,9.87c-.531.541-1.264.693-1.959.398-.695-.29-1.11-.925-1.11-1.687v-13.971ZM45.642,50.031c-3.069,2.4-6.711,3.944-10.528,4.46-.502.069-.989-.084-1.37-.428-.396-.349-.622-.856-.622-1.387v-13.971c0-.767.415-1.397,1.11-1.687.236-.098.473-.148.704-.148.463,0,.902.187,1.254.546l9.63,9.87c.362.374.555.89.521,1.416-.039.531-.285,1.003-.7,1.328ZM54.211,34.909c-.502,3.91-2.002,7.637-4.342,10.785-.314.423-.786.684-1.308.718-.516.039-1.028-.157-1.394-.536l-9.645-9.88c-.526-.541-.671-1.288-.386-1.992.289-.708.907-1.126,1.66-1.126h13.635c.521,0,1.013.231,1.361.629.338.393.487.89.42,1.402Z");
fill: white;
}
will give you these buttons:
For general-case vector images (and also for working with iOS, which does not support the CSS properties used above) the same can be done using CSS pseudo elements or simple JS
Not sure about external files from collections, but raw svg code can be used inside URL. I used to use this in one of my templates, so it certainly works:
.replay-button::after {
content: url("data:image/svg+xml,<svg viewBox='0 0 100 100' xmlns='http://www.w3.org/2000/svg'>...SVG CODE...</svg>");
}