Define colors centrally in administration

[f1sh1918]

Is your feature request related to a problem? Please describe.
Currently we have no defined colors file and some colors are defined custom via hex

Describe the solution you'd like

• define a colors file and use the variables in the project
• check if it makes more sense to constantly use the mui theme and just this, even it probably will make issues with blueprint js

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.