Help trying to figure out how to affect humanoids in touch functions?

First of all, you should put your code in a code block. Next, I don't completely know if I understood what you were trying to do correctly, but if I did this is how you would do it.

local myPart = Instance.new("Part",workspace)  -- create part
myPart.CFrame = CFrame.new(10, 0, 10)

function onTouch(myPart) -- touch function
	local Human = myPart.Parent:FindFirstChild("Humanoid")
	if Human then -- if humanoid exists to check if it's a player (so no error occurs)
		local Char = myPart.Parent -- get character
		local explosion = Instance.new("Explosion",myPart) -- create explosion
		explosion.Position = myPart.Position
		local BodyColors = Char:WaitForChild("Body Colors") -- get character's body colors (necessary to change color of characer)
		BodyColors.TorsoColor3 = Color3.fromRGB(255,0,0) -- change color to red
	end	
end

myPart.Touched:Connect(onTouch) -- connect touch function to touched event

The explosion kills the character almost instantly when you touch the part so the red torso is hard to see but it does change.