What kind of "opacity" styles are used in icons8 icons?

We embed the icons8 API into our product editor. We need the resulting colors to be solid. However, some of the icons use semi transparent values - ie the icons from the new “plumpy” icon set.
We will now try to handle them anyway by changing the opacity and set a defined color based on a given background color.

In your SVG I see:
<path d="M20,19H4c-..." opacity=".3"/>

Are there any other types of opacity attributes used in your icons? eg fill-opacity oder style="opacity:0.3"? If so, can you please name the types and give me some examples (Icon ID or URL)?
And are all icons with opacity used only on path elements? If not, may you give me some examples of these other usages?

If you have a good idea how to get full colored icons in the API, I am also interested to read.

Thanks a lot

Hi Daniel!

All “gray” objects in the Plumpy set use black with opacity set to 35%.

The objects in question can be of any shape (path, circle, rectangle, etc.). Since there’s thousands upon thousands of icons, it would be quite a workload to list them all or look for specific examples.