Setup custom style

As I have read here there was an option to configure your own style:
I can still take a look at my style but I cannot define it at the beginning. Is it even possible to specify that e.g. all company nodes are red, all employee nodes with a certain property are green? ...

At least I can take a look at the schema and setup the colors as required, but this is manual effort.

In the star tab I see the area to drop a .grass file, which means you can define your style in that format and drop it in.

node.Company {
  color: #A1B2C3;
node.Person {
  color: #D3D3D3;

or what have you, along with modifying any of the other options shown in that :style snippet you shared. I don't believe it is possible to define styles based on a certain property, just based on labels (or relationship type).