If '55-1st has a black rear floor mat, the same color as in 1954, then I bet the front floor mat is black.

The '54-'55-1st upholstery and cardboard door panels were also different colors from earlier years' suburbans.

1929-1954 Chevrolet Master Parts Catalog
Section 16.800 (Commercial Vehicles front floor mats)

3810590 1954 Suburban (front floor mat molded under the passenger seat.
3810690 1947-1953 Suburban (front floor mat molded under the passenger seat)

There was also a Suburban front floor mat available that apparently was not molded to go under the passenger seat.
1952-1953 3698175