Background colour

i have a small issue….

  • Grafana is working on a Docker on my synology NAS

For the visualisation i am using iobroker. So far so good.

I Need to Change the Background Color to black. If i see it Right, the Coluor is #161719

Can anybody help me to Change this Colour to #000000, easy and step by step? Sorry my skills are not very good. Thanks in adavance