wp-includes/theme.php:1193Displays the custom header text color in 3- or 6-digit hexadecimal form (minus the hash symbol).
function header_textcolor() { echo get_header_textcolor();}Introduced in 2.1.0. Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-includes/theme.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.