Put the following line of CSS into a tiddler tagged with $:/tags/Stylesheet:
[data-tags*="purple"] .tc-tiddler-body .tc-tiddlylink { color:purple; }
Alternatively, instead of using tags, you can use the value from a "linkcolor" field, like this:
<$list filter="[has[linkcolor]]">
<div>
[data-tiddler-title^="<<currentTiddler>>"] .tc-tiddler-body .tc-tiddlylink { color:{{{ [<currentTiddler>get[linkcolor]] }}}; }
</div>
</$list>
Notes:
* The $list find each tiddler that has non-blank linkcolor field
* The CSS defines a "data-tiddler-title" rule for each matching tiddler, where the color attribute value is retrieved from that tiddler's "linkcolor" field
* The <div>...</div> is not required, but simply puts the results for each matching tiddler on a separate line for easier reading
enjoy,
-e