user: Question: For which network was Chris Walby the color commentator after 1990?
Columns: ['Year', 'Network', 'Play-by-play', 'Colour commentator(s)', 'Pregame host']
Types: ['real', 'text', 'text', 'text', 'text']
Sample row: [1999.0, 'CBC', 'Chris Cuthbert', 'Chris Walby', 'Brian Williams']
SQL:

assistant: SELECT "Network" FROM "Table" WHERE "Year" > 1990.0 AND "Colour commentator(s)" = 'Chris Walby';