Step 1: Understand what the Red Data Book is.
The Red Data Book is a document published by the International Union for Conservation of Nature (IUCN).
Step 2: Recall its purpose.
It provides detailed information on:
endangered species,
threatened plants and animals,
risk status of species facing extinction.
Step 3: Eliminate incorrect options.
Red flowered plants — unrelated.
Red coloured fishes — unrelated.
Red eyed birds — unrelated.
Hence, the correct answer is
\[
\boxed{\text{Endangered plants and animals}}
\]