Can't find this anywhere, tried the popular online converters.
How do I easily convert
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ase and aco files are not images. They are application code of color definitions within Adobe applications.
There may be a way to convert them directly to images, but I think that may be unlikely since the ase/aco formats are proprietary.
There are some online tools to display the colors. Such as ...
You could then take a screenshot to get a PNG.
I also found this: https://www.reaconverter.com/convert/ase_to_png.html for ASE 2 PNG, but it requires the download of software. I don't, in any way, vouch for this software. There are additional software downloads out there and a simple internet search will present them.
These URLs were merely cursory finds via an internet search. There may be better tools out there. I have no affiliation with either link.