def get_gas_color_list(gas_list, gas_color_dict=None):
    """Map the gas name to preset color in gas_color_dict.

    Use the same color for the gas to make it consistence

    Args:
        gas_list: a name of the gas
        gas_color_dict(optional): color dictionary to map the gas to

    Returns: list
        a lit of color value

    """
    if gas_color_dict is None:
        gas_color_dict = {'PM2.5': '#0000ff',
                          'PM10': '#660099',
                          'O3': '#cc0033',
                          'CO': '#cc3300',
                          'NO2': '#669900',
                          'SO2': '#00ff00'}

    return [gas_color_dict[gas] if gas in gas_color_dict.keys()
            else 'royalblue' for gas in gas_list]