Tashana, use the function to define the line between Modern and Art quilts.
Modern quilts are primarily functional quilts. Their main purpose is function, not art. It's a key part of the movement's raison d'être and is included in the category description for the shows that are starting to have separate categories for Modern quilts. An example from the HMQS in Salt Lake City:
Modern: Quilts that are functional, include bold colors, and are inspired by modern design. Minimalism, asymmetry, expansive negative space, and alternate grid work are often a part of modern quilt compositions, as are improvisational piecing and solid fabric.
Art quilts, no matter the style, are primarily NOT functional quilts. Their main purpose is art, not function. It's the key part of their esthetic.
If your quilt is functional, includes bold colors, and is inspired by modern design (keeping in mind that mid-century modern and many other art styles are included in that), then I'd say you're good to go.