The RedWheelbarrow

From what i read about william carlos williams known as Imagist-influenced philosophy of “no ideas but in things" so his poem also represents this idea saying with it so much depends on i think he is trying to say that whatever we see we just might not to be see in other way and actually reality versus imagination on this poem. he explains the red wheelbarrow under rain and there is word 'glazed with the rain' and this sentence also makes the reader to think what he is trying to say. or is it just something else that he tries to mention? and the color red actually what does it symbolize?