Better not to use \textcolor along with maths over multiple line. You can use \color{<colorname>} instead, and limit the scope by grouping.
\documentclass[a4 paper,11pt]{article} \usepackage{ parskip } \usepackage{ blindtext } \usepackage[usenames, dvipsnames]{xcolor} \usepackage{showframe} \begin{document} \begingroup \color{NavyBlue} Insert problem description here. Along with some math: \[ 1 \neq 0 \] \endgroup \blindtext \end{document}