Red and Blue starts out like the familiar "roses are red, violets are blue" rhyme, then stops itself with a awkward little correction: "Hold up, I mean." That interruption signals a change. The speaker restarts in the past tense, and the cheerful love-rhyme becomes something looking backward. Roses "were" red, violets "were" blue, and the sweetness is remembered rather than present.
The last stanza makes the loss plain. The roses are shriveled, the blue is gone, and the flowers have disappeared. Then the final line lands with a jolt: "And i will be too." Following the pattern of the earlier lines, the speaker places themselves among the vanished things. The poem doesn't say why, so the line can be read as a sense of fading away, deep sadness, or something more serious. The mood is quiet and heavy, made sharper by the playful form it borrows. The lowercase "i" adds to the feeling of smallness. Because the rhyme is so light, the ending feels even more painful.