Hi Jaime Millan Conejero,

https://stackoverflow.com/questions/72273470/change-bar-chart-column-color-in-odoo

Based on your requirement may be help.

export const COLORS = [

    "#1f77b4",

    "#ff7f0e",

    "#aec7e8",

    "#ffbb78",

    "#2ca02c",

    "#98df8a",

    "#d62728",

    "#ff9896",

    "#9467bd",

    "#c5b0d5",

    "#8c564b",

    "#c49c94",

    "#e377c2",

    "#f7b6d2",

    "#7f7f7f",

    "#c7c7c7",

    "#bcbd22",

    "#dbdb8d",

    "#17becf",

    "#9edae5",

];

This is Color list use Odoo  by deafult 

addons/web/static/src/views/graph/colors.js

Thanks.