A: The last two sentences of the poem express that the poet's mood has changed from relative calm to a little restless, from the original faint loneliness to a little cold.
Brief analysis: the last two sentences of the poem describe that when the poet was excited by things and felt lonely, he suddenly saw a woman in red tea leaning against the railing on the small building by the river. The pictures described in the three or four sentences are bright in color and full of painting, so we might as well appreciate them as a painting of Jiangnan water town customs. When a guest is lonely, his mood is a bit dull. Suddenly seeing such a beautiful picture makes me feel refreshed, and the loneliness of the journey seems to have been diluted a lot.