It is true that the green chemicals are performing a positive action in trying to put out the fire. We learn that in response to the rapidly spreading flames, the chemicals are brought in as reinforcements to the ineffective water rats and water sprays:
From attic trapdoors, blind robot faces peered down with faucet mouths gushing green chemical.
The image above has an unpleasant association to vomiting, though we might imagine the fire-fighting chemical as bright green.
This negative portrayal of the flame retardant is consistent with the theme of the story: too much technology is a danger to humankind. Bradbury portrays a world in which technology is controlling humans and not vice versa. The house does everything for its now dead occupants, and the power of nuclear weapons has gone out of control, apparently wiping out the entire society.
Referencing Sara Teasdale's cautionary poem, which has the same name as his story, Bradbury warns that in the end, our technology must align itself with natural forces. Nature is stronger than our technology, as illustrated by the fire burning down the house. Nature, in the end, will do what it wants, regardless of human wishes. If we destroy ourselves, both the story and the poem assert, that natural world will go on about its business, utterly uncaring about humans.