Modern Technical Manual & Field Guide

\documentclass[11pt,a4paper,oneside,headings=big,chapterprefix=true]{scrreprt}

% ---------- Core packages ----------
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage[left=2.6cm,right=2.6cm,top=2.8cm,bottom=2.8cm,headheight=28pt]{geometry}
\usepackage{amsmath}
\usepackage{amssymb}
\usepackage{xcolor}
\usepackage[table]{xcolor}
\usepackage{graphicx}
\usepackage{booktabs}
\usepackage{colortbl}
\usepackage{array}
\usepackage{tabularx}
\usepackage{enumitem}
\usepackage{tikz}
\usetikzlibrary{positioning,calc,shapes.geometric,decorations.pathmorphing,backgrounds,patterns}
\usepackage[most]{tcolorbox}
\usepackage{fontawesome5}
\usepackage{scrlayer-scrpage}
\usepackage{hyperref}

% ---------- Palette ----------
\definecolor{steel}{RGB}{33,69,94}
\definecolor{amberaccent}{RGB}{198,138,42}
\definecolor{fogbg}{RGB}{238,241,243}
\definecolor{inkgray}{RGB}{45,49,54}

% ---------- Typography ----------
\addtokomafont{disposition}{\color{steel}}
\addtokomafont{chapter}{\color{steel}\bfseries}
\addtokomafont{chapterprefix}{\normalfont\normalsize\color{amberaccent}\bfseries}
\setkomafont{chapterentry}{\color{steel}}
\setkomafont{caption}{\small\color{inkgray}}
\setkomafont{captionlabel}{\small\bfseries\color{steel}}
\renewcommand*{\chapterformat}{\mbox{\chapappifchapterprefix{\ }\thechapter\autodot\enskip}}

\clearpairofpagestyles
\ihead{\small\color{steel}\slshape\leftmark}