Bar plot does not use defined color cycle list

The pgfplots manual (v1.17 (2020/02/29), page 214) notes the following:

Thus, the currently active cycle list will be used if you write either addplot+[〈keys〉] ...; or if you don't use square brackets as in addplot[〈explicit plot specification〉]...;

Although the explanation is not very clear, this implies that you should remove the square brackets, as they overwrite the currently active cycle list:

documentclass{standalone}

usepackage{pgfplots}

pgfplotsset{/pgfplots/bar cycle list/.style={/pgfplots/cycle list={
            {blue,fill=blue!30!white,mark=none},
            {red,fill=red!30!white,mark=none},
            {brown!60!black,fill=brown!30!white,mark=none},
            {black,fill=gray,mark=none},},},}

begin{document}
    begin{tikzpicture}
    begin{axis}[ybar,enlargelimits=0.15]
    addplot coordinates{(5,10) (10,15) (15,5) (20,24) (25,30)};
    addplot coordinates{(5,3) (10,5) (15,15) (20,20) (25,35)};
    end{axis}
    end{tikzpicture}
end{document}

The list can also be stored first and then used by a bar plot later. Storing a list is done using the command pgfplotscreateplotcyclelist{listname}{list specification}, which can be used with the axis option cycle list name.

MWE (result is the same as above):

documentclass{standalone}

usepackage{pgfplots}

pgfplotscreateplotcyclelist{customlist}{
             {blue,fill=blue!30!white,mark=none},
             {red,fill=green!30!white,mark=none},
             {brown!60!black,fill=brown!30!white,mark=none},
             {black,fill=gray,mark=none}
}

begin{document}
    begin{tikzpicture}
    begin{axis}[ybar,enlargelimits=0.15,cycle list name=customlist]
    addplot coordinates{(5,10) (10,15) (15,5) (20,24) (25,30)};
    addplot coordinates{(5,3) (10,5) (15,15) (20,20) (25,35)};
    end{axis}
    end{tikzpicture}
end{document}

---

If you want to use a custom list by name in pgfplotsset then you need the syntax /pgfplots/bar cycle list/.style={/pgfplots/cycle list name={listname}}. This setting will remain in effect until a new list is loaded, without needing to specify it as an option for individual plots.

MWE:

documentclass{standalone}

usepackage{pgfplots}

pgfplotscreateplotcyclelist{customlist}{
             {blue,fill=blue!30!white,mark=none},
             {orange,fill=orange!30!white,mark=none},
             {brown!60!black,fill=brown!30!white,mark=none},
             {black,fill=gray,mark=none}
}

pgfplotscreateplotcyclelist{otherlist}{
             {blue,fill=blue!30!white,mark=none},
             {green,fill=green!30!white,mark=none},
             {brown!60!black,fill=brown!30!white,mark=none},
             {black,fill=gray,mark=none}
}

pgfplotsset{/pgfplots/bar cycle list/.style={/pgfplots/cycle list name={otherlist}}}

begin{document}
    begin{tikzpicture}
    begin{axis}[ybar,enlargelimits=0.15]
    addplot coordinates{(5,10) (10,15) (15,5) (20,24) (25,30)};
    addplot coordinates{(5,3) (10,5) (15,15) (20,20) (25,35)};
    end{axis}
    end{tikzpicture}

    begin{tikzpicture}
    begin{axis}[ybar,enlargelimits=0.15]
    addplot coordinates{(5,10) (10,15) (15,5) (20,24) (25,30)};
    addplot coordinates{(5,3) (10,5) (15,15) (20,20) (25,35)};
    end{axis}
    end{tikzpicture}
    
pgfplotsset{/pgfplots/bar cycle list/.style={/pgfplots/cycle list name={customlist}}}

    begin{tikzpicture}
    begin{axis}[ybar,enlargelimits=0.15]
    addplot coordinates{(5,10) (10,15) (15,5) (20,24) (25,30)};
    addplot coordinates{(5,3) (10,5) (15,15) (20,20) (25,35)};
    end{axis}
    end{tikzpicture} 

end{document}

Result: