How can I select multiple parts via scripting ?

So today I was trying to make a script where there are white parts (DayBrick) and black parts (NightBrick). I wanted to make a script where on a ScreenGui button click any of the bricks disappear (NOTE: There are mutliple parts named 'NightBrick' and 'DayBrick'). The script is set as a Script and put into Workspace. The goal is that the script must detect all of the parts named each of them and change what they do/are.

Day = game.StarterGui.ScreenGui.DayButton
Night = game.StarterGui.ScreenGui.NightButton
DayBrick = game.Workspace.DayBrick
NightBrick = game.Workspace.NightBrick

Day.MouseButton1Click:connect(function()
	for _,Part in next, (game.Workspace:GetChildren()) do
    	if (Part .Name == "DayBrick") and Part :IsA("BasePart")  then
		DayBrick.Transparency = 0
		DayBrick.CanCollide = true
		NightBrick.Transparency = 1
		NightBrick.CanCollide = false
		end
	end
end)

Night.MouseButton1Click:connect(function()
	for _,Part in next, (game.Workspace:GetChildren()) do
    	if (Part .Name == "NightBrick") and Part :IsA("BasePart")  then
		DayBrick.Transparency = 1
		DayBrick.CanCollide = false
		NightBrick.Transparency = 0
		NightBrick.CanCollide = true
		end
	end
end)

You can just use pairs in a for loop. I usually never use next.

Also, I think it'd be a lot easier if you made two seperate folder instances and put the two different types of bricks in each instead of getting all the children of the entire workspace.

Day = game.StarterGui.ScreenGui.DayButton
Night = game.StarterGui.ScreenGui.NightButton
DayFolder = game.Workspace.DayFolder:GetChildren()--day bricks are inside here
NightFolder = game.Workspace.NightFolder:GetChildren()--night bricks are inside here

Day.MouseButton1Click:connect(function()--Notice that I took out the if function because we already can assume any parts inside the day folder are only a day block.
    for key,Part in pairs(DayFolder) do
        Part.Transparency = 0
        Part.CanCollide = true
        Part.Transparency = 1
        Part.CanCollide = false
    end
end)

Night.MouseButton1Click:connect(function() --Notice that I took out the if function because we already can assume any parts inside the night folder are only a night block.
    for key,Part in pairs(NightFolder) do 
        Part.Transparency = 1
        Part.CanCollide = false
        Part.Transparency = 0
        Part.CanCollide = true
    end
end)

Thank you for the script,I made slight changes (the time), but I found that when I click on 'Day' then the DayBlocks disappear, click on 'Night' - nothing happens + on daytime, the night blocks disappear and on nighttime, the dayblocks disappear, just to make it more correct. (It's a puzzle-adventure game I'm making)

Day = script.Parent.DayButton
Night = script.Parent.NightButton
DayFolder = game.Workspace.DayFolder:GetChildren()
NightFolder = game.Workspace.NightFolder:GetChildren()

Day.MouseButton1Click:connect(function()
    for key,Part in pairs(DayFolder) do
        Part.Transparency = 0	--Why is there 4 rows of 'Part.' ?
        Part.CanCollide = true	--Same
        Part.Transparency = 1	--Same
        Part.CanCollide = false  	--Same
		game.Lighting.TimeOfDay = '14:00:00'
    end
end)

Night.MouseButton1Click:connect(function()
    for key,Part in pairs(NightFolder) do 
        Part.Transparency = 1
        Part.CanCollide = false
        Part.Transparency = 0
        Part.CanCollide = true
		game.Lighting.TimeOfDay = '00:00:00'
    end
end)