I would like to:
omit the page number from parts pages
provide some changes in the title style of the part page.

Here is a MWE:
\documentclass[french,12pt,oneside,openright]{memoir}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{lmodern}
\usepackage[sonny]{fncychap}
\usepackage{usnomencl}%pour la nomenclature
\usepackage{pgfplots}
\usepackage{titlesec, blindtext, color}
