currentColor is SVG specific. It is not a TW variable.
Within SVGs you can not use the colour macro. But there have been some discussions where
Eric Shulman posted functions, similar to those below. So you can create a new tiddler and tag it $:/tags/Global so you should be able to use colour palette values.
title: get-colour-functions
tags: $:/tags/Global
code-body: yes
\define colorRegexp() <<(get)?[cC]olou?r .*>>
\function f.getColor(c) [{$:/palette}getindex<c>] ~[[$:/palettes/Vanilla]getindex<c>] ~[[$:/config/DefaultColourMappings/]addsuffix<c>get[text]] :map[function[recolor],<currentTiddler>]
\function f.getColour(c) [function[getColor],<c>]
\function recolor(c) [<c>regexp<colorRegexp>] :then[<c>split[ ]last[]trim[']trim["]trim[>>]] :map[function[getColor],<currentTiddler>] :else[<c>]
In your SVG you can do the following. The icon SVGs have a strange viewBox. So I did change that one too. The code below should work. It did for me.
title: $:/themes/telumire/images/boxicons/regular/checkbox-square.svg
\parameters (size:"24")
<svg width=<<size>> height=<<size>> class="tc-image-bxi-bx-checkbox-square tc-image-button" viewBox="0 0 24 24">
<g fill-rule="evenodd" >
<path d="M9 9H15V15H9z" fill=<<f.getColor "alert-highlight">>/>
<path fill=<<f.getColor "primary">>
d="M19,17V7c0-1.103-0.897-2-2-2H7C5.897,5,5,5.897,5,7v10c0,1.103,0.897,2,2,2h10C18.103,19,19,18.103,19,17z M7,7h10 l0.002,10H7V7z"/>
</g>
</svg>