simworld.cc (https://github.com/aburch/simutrans/blob/f40e4cda83e791e6f2c91b0d5396e8b08b914492/src/simutrans/world/simworld.cc) line: https://github.com/aburch/simutrans/blob/f40e4cda83e791e6f2c91b0d5396e8b08b914492/src/simutrans/world/simworld.cc#L2992 (https://github.com/aburch/simutrans/blob/f40e4cda83e791e6f2c91b0d5396e8b08b914492/src/simutrans/world/simworld.cc#L2992)
msg->add_message(buf,koord::invalid,message_t::general,color_idx_to_rgb(COL_BLACK),skinverwaltung_t::neujahrsymbol->get_image_id(0));
change COL_BLACK to SYSCOL_TEXT
Thank you found another location (text on missing gadgets).