The poem Red is a subjective truth or perspective communicating to us through the powerful symbol of colours. The poem was written in the last months of their marriage and it is also a last look of their marriage. The symbol 'red' is the colour that Plath liked but in hughes perspective he saw it as death and fire. Plath has a battle with death and calmness, as seen in stanza 6 ' everything you painted you painted white, then splashed it with roses' it means she was calm while painting, but then she wanted roses for warmth.
i hope this helps, i have more but if you need the techniques and other things just PM me or reply to this.