so modern Marshall grill cloth looks brownish is that because they use black and cream as opposed black and white?Those are basketweave.
Marshall used basketweave from early 1968 through to April 1971. The pinstripe was earlier - mid 1965 to early 1968.
What you have to remember is the basketweave material was black and white originally, so it looks grey in old photos and film footage. That's how it looked originally. It only goes brown with age.
Here is a piece removed from a cab. Notice how the edges and under the logo are still black and white where it hasn't been exposed to the elements: