Blender: show current mode with status bar colors

status_bar_mode_color.py

bl_info = {
    "name": "Status Bar Mode Color",
    "author": "Dspazio / vfig",
    "version": (1, 0),
    "blender": (2, 80, 0),
    "location": "View3D",
    "description": "Changes background gradient color for each mode.",
    "warning": "",
    "doc_url": "",
    "category": "Themes",
}

import bpy
from bpy.app.handlers import persistent

# nice green: 33b061
COLORS_BY_MODE = {
    # mode               header    text      highlight
    'default':          ('000080', '00cccc', '00ffff'),
    'OBJECT':           ('303030', 'cccccc', 'ffffff'),
    'EDIT':             ('ff9e00', '101010', '000000'),
    'POSE':             ('ff0080', '101010', '000000'),
    'SCULPT':           ('59e5ff', '101010', '000000'),
    'VERTEX_PAINT':     ('9400d3', 'eeeeee', 'ffffff'),
    'WEIGHT_PAINT':     ('ffffff', '101010', '000000'),
    'TEXTURE_PAINT':    ('008080', 'eeeeee', 'ffffff'),
    }

def srgb_to_linearrgb(c):
    if   c < 0:       return 0
    elif c < 0.04045: return c/12.92
    else:             return ((c+0.055)/1.055)**2.4

def hex_to_rgb(h):
    if isinstance(h, str):
        if h.startswith('#'):
            h = h[1:]
        h = int(h, 16)
    r = (h & 0xff0000) >> 16
    g = (h & 0x00ff00) >> 8
    b = (h & 0x0000ff)
    return tuple([srgb_to_linearrgb(c/0xff) for c in (r,g,b)])

def hex_to_rgba(h,alpha=1):
    if isinstance(h, str):
        if h.startswith('#'):
            h = h[1:]
        h = int(h, 16)
    r = (h & 0xff0000) >> 16
    g = (h & 0x00ff00) >> 8
    b = (h & 0x0000ff)
    return tuple([srgb_to_linearrgb(c/0xff) for c in (r,g,b)] + [alpha])

@persistent
def set_status_bar_color(scene):
    obj = bpy.context.active_object
    if obj:
        color_hex = COLORS_BY_MODE.get(obj.mode, COLORS_BY_MODE['default'])
        statusbar = bpy.context.preferences.themes[0].statusbar.space
        statusbar.header = hex_to_rgba(color_hex[0])
        statusbar.header_text = hex_to_rgb(color_hex[1])
        statusbar.header_text_hi = hex_to_rgb(color_hex[2])
    
def register():
    bpy.app.handlers.depsgraph_update_post.append(set_status_bar_color)

def unregister():
    bpy.app.handlers.depsgraph_update_post.remove(set_status_bar_color)

if __name__ == "__main__":
    register()