The poem sets two questions side by side. The first is almost playful: when you say you love the sky, is it the sky itself you love, or just the color blue that comes with it? The second question drops the playfulness. The speaker asks someone close, "Do you love me, or the things I do?"
The comparison does the work. Blue is only a surface quality of the sky, something we notice first and mistake for the whole thing. In the same way, the speaker worries that a partner or loved one might care about their actions, achievements, or usefulness rather than who they are underneath.
The speaker sounds quiet, a little vulnerable, and unsure. There's no anger, just a wish to be seen fully. The short lines and simple rhyme of "do" and "blue" give the poem a soft, wondering mood, like a thought spoken aloud at the end of a long day. It leaves the question hanging, and that uncertainty is what stays with you.