Misc: One who fought professionally in Roman arenas was a(n) ?

Questions

What colour would one associate with the Spanish volunteer force on the eastern front in the WWII?

What colourless, odourless light gas is used to lift airships?

What common dog breed takes its name from the fact that they were originally bred to hunt a game bird called "woodcocks"?

What company created a computer dubbed Jackintosh?

What company invented abs brakes for cars?