How do you change multiple bricks color in a model?

Do you have to do them separately?

I'm making a hologram game.

When the orange button has been pressed, it lights up the other brick so you can walk to the other side of the map.

Not exactly sure what you're asking, but based on the title you provided, it should look something like this:

newColor = BrickColor.new("Really red");

model = game.Workspace.MyModel;

for i, v in ipairs(model:GetChildren()) do
	if(v:IsA("Part") or v:IsA("BasePart")) then
		v.BrickColor = newColor;
	end
end