For python openpyxl, translates a cells theme and tint to an rgb color code.

openpyxl_theme_and_tint_to_rgb.py

# found at: https://pastebin.com/B2nGEGX2, WRT https://stackoverflow.com/a/58443509/1787137

from colorsys import rgb_to_hls, hls_to_rgb
#https://bitbucket.org/openpyxl/openpyxl/issues/987/add-utility-functions-for-colors-to-help

RGBMAX = 0xff  # Corresponds to 255
HLSMAX = 240  # MS excel's tint function expects that HLS is base 240. see:
# https://social.msdn.microsoft.com/Forums/en-US/e9d8c136-6d62-4098-9b1b-dac786149f43/excel-color-tint-algorithm-incorrect?forum=os_binaryfile#d3c2ac95-52e0-476b-86f1-e2a697f24969

def rgb_to_ms_hls(red, green=None, blue=None):
    """Converts rgb values in range (0,1) or a hex string of the form '[#aa]rrggbb' to HLSMAX based HLS, (alpha values are ignored)"""
    if green is None:
        if isinstance(red, str):
            if len(red) > 6:
                red = red[-6:]  # Ignore preceding '#' and alpha values
            blue = int(red[4:], 16) / RGBMAX
            green = int(red[2:4], 16) / RGBMAX
            red = int(red[0:2], 16) / RGBMAX
        else:
            red, green, blue = red
    h, l, s = rgb_to_hls(red, green, blue)
    return (int(round(h * HLSMAX)), int(round(l * HLSMAX)), int(round(s * HLSMAX)))

def ms_hls_to_rgb(hue, lightness=None, saturation=None):
    """Converts HLSMAX based HLS values to rgb values in the range (0,1)"""
    if lightness is None:
        hue, lightness, saturation = hue
    return hls_to_rgb(hue / HLSMAX, lightness / HLSMAX, saturation / HLSMAX)

def rgb_to_hex(red, green=None, blue=None):
    """Converts (0,1) based RGB values to a hex string 'rrggbb'"""
    if green is None:
        red, green, blue = red
    return ('%02x%02x%02x' % (int(round(red * RGBMAX)), int(round(green * RGBMAX)), int(round(blue * RGBMAX)))).upper()


def get_theme_colors(wb):
    """Gets theme colors from the workbook"""
    # see: https://groups.google.com/forum/#!topic/openpyxl-users/I0k3TfqNLrc
    from openpyxl.xml.functions import QName, fromstring
    xlmns = 'http://schemas.openxmlformats.org/drawingml/2006/main'
    root = fromstring(wb.loaded_theme)
    themeEl = root.find(QName(xlmns, 'themeElements').text)
    colorSchemes = themeEl.findall(QName(xlmns, 'clrScheme').text)
    firstColorScheme = colorSchemes[0]

    colors = []

    for c in ['lt1', 'dk1', 'lt2', 'dk2', 'accent1', 'accent2', 'accent3', 'accent4', 'accent5', 'accent6']:
        accent = firstColorScheme.find(QName(xlmns, c).text)

        if 'window' in accent.getchildren()[0].attrib['val']:
            colors.append(accent.getchildren()[0].attrib['lastClr'])
        else:
            colors.append(accent.getchildren()[0].attrib['val'])

    return colors

def tint_luminance(tint, lum):
    """Tints a HLSMAX based luminance"""
    # See: http://ciintelligence.blogspot.co.uk/2012/02/converting-excel-theme-color-and-tint.html
    if tint < 0:
        return int(round(lum * (1.0 + tint)))
    else:
        return int(round(lum * (1.0 - tint) + (HLSMAX - HLSMAX * (1.0 - tint))))

def theme_and_tint_to_rgb(wb, theme, tint):
    """Given a workbook, a theme number and a tint return a hex based rgb"""
    rgb = get_theme_colors(wb)[theme]
    h, l, s = rgb_to_ms_hls(rgb)
    return rgb_to_hex(ms_hls_to_rgb(h, tint_luminance(tint, l), s))

THX

@Mike-Honey is this code licensed or can we use it freely?

@yairogen I don't see any problem with that. As noted at the top, the original source was StackOverflow. All user content there is implicitly licensed as Creative Commons.
https://stackoverflow.com/legal/terms-of-service/public#licensing

I have this problem when I use accent.getchildren()... it says xml.etree.ElementTree.Element object has no attribute 'getchildren'. Anybody knows how to solve this?

@EmDem6 use list(accent) instead