hot.py

#!/bin/python3

import openrgb, glob

C = openrgb.utils.RGBColor

o = openrgb.OpenRGBClient()
d = o.devices[0]
z = d.zones[0]

d.set_mode(0)

while True:
  t = max([int(open(i).read()) for i in glob.glob('/sys/class/hwmon/hwmon?/temp?_input')])/1000
  i = int(max(0,min(255, (t-30) / 60 * 256)))
  c = C(i, 255-i, 0)
  # print('t = %5.2f°C; i = %d; c = %s' % (t, i, c))
  z.set_color(c)

hot.service

[Unit]
Description=Hot (temps => RGB)
Wants=openrgb.service
After=openrgb.service

[Service]
ExecStart=/home/peter/bin/hot.py
Restart=on-failure
User=peter

[Install]
WantedBy=multi-user.target

openrgb.service

[Unit]
Description=OpenRGB server

[Service]
ExecStart=/home/peter/OpenRGB/OpenRGB --server
ExecStartPost=sh -c 'until lsof -i :6742; do sleep .1; done;'
Restart=on-failure

[Install]
WantedBy=multi-user.target