Needle normal script not runningto make a needle show if you have a tool part have a certain color?

You cannot get the LocalPlayer from a Server Script. The LocalPlayer can only be called by a Local Script.

Also, if you have 'player' as a parameter, you won't probably need LocalPlayer since you can get the player that clicked the ClickDetector from that parameter.

function OnClicked(player) --[[ you have player as the parameter, this will automatically return the player that clicked on the ClickDetector.]]
local Plr = game.Players.LocalPlayer --[[ can't get LocalPlayer from a Server Script (Normal Script). ]]
if Plr.Backpack.Collector.MovingParts.Change.Color == "Crimson" then
print(player.Name.." clicked on blood extract.") 
local needle = script.Parent:WaitForChild("Needle")
needle.Change.Transparency = 0
needle.NeedleGlass.Transparency = 0.3   
elseif Plr.Backpack.Collector.MovingParts.Change.Color == "Fossil"  then
print("Player has no blood needle")
end
end

script.Parent.ClickDetector.MouseClick:connect(OnClicked) 

If you want to run this in a Server Script, then the script would probably go like this:

function OnClicked(player)
if player.Backpack.Collector.MovingParts.Change.Color == "Crimson" then
print(player.Name.." clicked on blood extract.") 
local needle = script.Parent:WaitForChild("Needle")
needle.Change.Transparency = 0
needle.NeedleGlass.Transparency = 0.3   
elseif player.Backpack.Collector.MovingParts.Change.Color == "Fossil"  then
print("Player has no blood needle") --[[ if you want this to print the player that clicked on the ClickDetector, it'll be print(player.Name.." has no blood needle")]]
end
end

script.Parent.ClickDetector.MouseClick:connect(OnClicked) 

Remember, you cannot get the LocalPlayer from a Server Script (Normal, not Local Script).