Why is my door not opening?

Make two separate functions.

Base = game.Workspace.Part
Colors = game.Workspace.Parts

--function onTouched(hit)

--end

--function onTouchEnded(hit)

--end
-- I'm using the comment feature to highlight the things that are added on to the script.

Make 2 connection lines for those functions.

Base = game.Workspace.Part
Colors = game.Workspace.Parts

function onTouched(hit)

end

function onTouchEnded(hit)

end

--script.Parent.Touched:connect(onTouched)
--script.Parent.TouchEnded:connect(onTouchEnded)

Fill in your code.

Base = game.Workspace.Part
Colors = game.Workspace.Parts

function onTouched(hit)
--	Base.Transparency = .5
--	Base.CanCollide = false
--	Colors.BrickColor = BrickColor.new("Bright green")
end

function onTouchEnded(hit)
--	Base.Transparency = 0
--	Base.CanCollide = true
--	Colors.BrickColor = BrickColor.new("Bright red")
end

script.Parent.Touched:connect(onTouched)
script.Parent.TouchEnded:connect(onTouchEnded)

Utilize the 'hit' argument if you don't want a random part to touch the parent of script.

Base = game.Workspace.Part
Colors = game.Workspace.Parts

function onTouched(hit)
--	if (hit and hit.Parent and hit.Parent:FindFirstChild("Humanoid")) then
		Base.Transparency = .5
		Base.CanCollide = false
		Colors.BrickColor = BrickColor.new("Bright green")
--	end
end

function onTouchEnded(hit)
--	if (hit and hit.Parent and hit.Parent:FindFirstChild("Humanoid")) then
		Base.Transparency = 0
		Base.CanCollide = true
		Colors.BrickColor = BrickColor.new("Bright red")
--	end
end

script.Parent.Touched:connect(onTouched)
script.Parent.TouchEnded:connect(onTouchEnded)

If "Base" is the door, and you want the player to touch the door to activate its functions, you can do this if the script is in another location.

Base.Touched:connect(onTouched)
Base.TouchEnded:connect(onTouchEnded)

There's this amazing thing called a "Model." It's an object that can group things together, so they'd be relatively separate from other objects in terms of scripting. I would recommend grouping all of the parts that have anything to do with the door such as the indicator and the door part. Doing so will help in terms of organization.

If you do that, you can also set the script to be in the model and adjust your variables so it would be like this:

Base = script.Parent.Part
Colors = script.Parent.Parts

That way your script will access to your parts internally (from the scripts' point of view) rather than externally (from the game's point of view).