In the First Pompeian Style, artists inspired themselves to marble or precious stones, using bold colors to suggest richness and importance.

Image source: https://en.wikipedia.org/wiki/Bilbilis_(Augusta_Bilbilis)#/media/File:Calatayud_-_Museo_de_Calatayud_-_Cubiculo.jpg
Painting as an Illusion
The First style was also structural or masonry style is characterized by the simulation of marble veneering, with other elements taken from other cultures like alabaster discs with vertical lines, ‘wooden’ beams in yellow, and ‘pillars’ and ‘cornices’ in white. It also uses vivid color which was considered a sign of richness.
Image source: https://search.creativecommons.org/photos/6ab0bce0-504a-4105-9c48-796361a3f9b0 by Following Hadrian
This style used to divide walls into several patterns used to replace much more expensive cut stones. The First Style was also used to create fusions with other conceivings of art to decorate the bottom parts of the walls that were not important as the higher ones. The image below is a replica of that found in the Ptolemaic palaces, where the walls were made colorful with real marble stones.
Image source: https://en.wikipedia.org/wiki/House_of_Sallust#/media/File:Casa_di_Sallustio_1.JPG
To create the illusion of a wall composed of blocks, stucco was first applied to the wall and the shapes of stone blocks were given to it and pilasters and moldings. Artisans then used paint to cover up the stucco in many colorful marble-like patterns. These wall paintings were affordable but they were not considered cheap substitutes. Creating these paintings required several hours of hard work.
From Greece to Rome
This style was inspired by the Ptolemaic palaces, where walls were inset with real stones and marbles. They used bold colors to recall precious materials, this idea was a simulation of the art of Hellenistic kingdoms in the late 4th to early 3rd century B.C. The Ptolemaic loved luxury in general and expressed this passion through the Greek style in its magnificent and luxurious complexes.
Quality Decoration at Cheaper Cost
Ordinary Romans could not afford expensive materials to improve the look of the walls inside their estates, so they decorated their homes with painted imitations of the luxurious yellow, purple and pink marbles. Painters developed good skills in imitating marbles and rectangular slabs were rendered pretty well on the walls and looked as marbled and veined as real pieces of stone.

Image source: https://search.creativecommons.org/photos/4bc89bae-09cd-4176-9d2c-0a21cce96e9c by ell brown

Image source: https://search.creativecommons.org/photos/a33126fb-6262-49d4-bca7-4a1367d22c9c by ell brown
Great examples of the First Pompeian Style are the House of the Faun and the House of Sallust, places that you can visit in Pompeii. The House of the Faun was built during the 2nd century BC, it was one of the most important private estates in Pompeii talking about the artistic relics found inside the mansion.

Image source: https://search.creativecommons.org/photos/8cb09ac3-d8e6-4034-8b84-e64b04680a33 by kudumomo

Image source:https://search.creativecommons.org/photos/81ec0529-7eae-413e-8b44-611595cf33a5 by kudumomo
Info source:
https://www.britannica.com/place/ancient-Egypt/Macedonian-and-Ptolemaic-Egypt-332-30-bce