RGB Pixel color of location

Hi there.. Wondering how do I get pixel color of an location if the color math then do.. if not dont do action?

I had try using
if exists("Image.png") 
getLastMatch():highlight(0.1) -- highlight what's found

image = (getLastMatch()) 
click(image,1)
else
wait(0.1)
end

but it seems even the image is not exists.. it still clicks.

Any idea how to improve?