This is the 850th most frequent Italian word.
giallo
"Yellow" (color) or "mystery" (genre).
Here, 'giallo' describes the color of the sun.
Il sole oggi è così giallo e brillante.
Today the sun is so yellow and bright.
'Giallo' here denotes the color of the traffic light indicating caution.
Il semaforo è giallo, prepara a fermarti.
The traffic light is yellow, prepare to stop.
In this context, 'giallo' refers to a mystery or crime novel, a specific genre.