newlist{MyList}{enumerate}{2}
setlist[MyList,1]{label={arabic*.}, resume}% ALWAYS resumed

newenvironment{MyColoredList}[2][]{%
    color{#2}%
    begin{MyList}[#1]
}{%
    end{MyList}%
}%

documentclass{article}
usepackage{enumitem}
usepackage{xcolor}

newlist{MyList}{enumerate}{2}
setlist[MyList,1]{label={arabic*.}, resume}% ALWAYS resumed
setlist[MyList,2]{label={alph*)}}%           NOT resumed

newenvironment{MyColoredList}[2][]{%
    color{#2}%
    begin{MyList}[#1]
}{%
    end{MyList}%
}%


begin{document}
    begin{MyColoredList}{red}
        item First Item
    end{MyColoredList}
    Some text
    begin{MyColoredList}{orange}
        item First Item
    end{MyColoredList}
    Some text
    begin{MyList}
        item Second Item
    end{MyList}
    Some text
    begin{MyList}
        item Third Item
    end{MyList}
    Some text
    begin{MyColoredList}{blue}
        item Fourth Item (this works!!)
    end{MyColoredList}
end{document}