Citing Po Lu, who kindly fixed part of the issue[2]:

    I see the problem, or rather, two distinct problems, the one being
    that the cursor face is flatly ignored when a stipple pattern is
    present, which I've just fixed, the other that the colors of such a
    stipple pattern are fixed to the image's background color and a
    black foreground, rather than adapting to the colors of the face in
    which it is displayed.  Here my scant knowledge of matters Nextstep
    failed me, and as such I will leave this to someone else with more
    experience than I.

This report is about the second part described above.

Best, Arash

Footnotes:
[1]  https://github.com/jdtsmith/indent-bars#stipples
[2]  https://lists.gnu.org/archive/html/emacs-devel/2024-05/msg00103.html


In GNU Emacs 30.0.50 (build 1, aarch64-apple-darwin23.4.0, NS
 appkit-2487.50 Version 14.4.1 (Build 23E224)) of 2024-05-02 built on
 MacMutant.fritz.box
Repository revision: ef6ffbdc79645e719d3b5ef23c9200405c58c61e
Repository branch: master
Windowing system distributor 'Apple', version 10.3.2487
System Description:  macOS 14.4.1

Configured using:
 'configure --with-ns --without-pop --without-mailutils --with-threads
 --with-modules --with-native-compilation --without-compress-install
 'CFLAGS=-O2 -g0 -pipe''

Configured features:
ACL GLIB GMP GNUTLS LCMS2 LIBXML2 MODULES NATIVE_COMP NOTIFY KQUEUE NS
PDUMPER PNG RSVG SQLITE3 THREADS TOOLKIT_SCROLL_BARS TREE_SITTER WEBP
XIM ZLIB