If you're aiming to build a strong investment portfolio, then it is usually a good idea to include a few blue chips in there.

But which blue chip ASX 200 shares could be buys in October? Here are four that are rated highly by analysts:

Brambles Limited (ASX: BXB)

The first ASX 200 blue chip share that could be a buy is Brambles. It is a supply chain solutions company that manages the world's largest pool of reusable pallets, crates, and containers.

Ord Minnett is positive on the company and believes that the company is well-placed for growth. This is partly due to its Serialisation Plus plan, which is aiming to make its operations more efficient.

The broker currently has a buy rating and $20.80 price target on Brambles' shares.

CSL Limited (ASX: CSL)

The team at Bell Potter thinks that CSL could be an ASX 200 blue share to buy now. It is one of the world's leading biotechnology companies with a collection of high-quality businesses across plasma therapies, vaccines, and iron deficiency therapies.

Bell Potter believes now would be a great time to snap up its shares. Earlier this week, it stated that it thinks the "stock looks undervalued on a PE ratio 18%/8% below 5yr/10yr historical averages and is set for double-digit earnings growth driven by the core Behring division."

Bell Potter has a buy rating and $345.00 price target on its shares.

Goodman Group (ASX: GMG)

A third ASX 200 blue chip share that could be worth considering is Goodman Group.

It is a leading integrated commercial and industrial property company that owns, develops, and manages high-quality, sustainable properties. These are found close to consumers and provide essential infrastructure for the digital economy.

Morgan Stanley is bullish on the company and continues to forecast solid earnings growth in the coming years. It has an overweight rating and $42.00 price target on its shares.

Woolworths Limited (ASX: WOW)

Finally, Goldman Sachs think that Woolworths could be a great ASX 200 blue chip share to buy now. It is of course Australia's largest retailer and one of the big two supermarket operators.

The broker believes Woolworths is well ahead of the competition. So much so, its analysts "continue to believe WOW has a multi-year advantage in terms of scale and industry knowledge vs. key industry peers that will help to better insulate it against Amazon risk vs. peers."

Goldman currently has a buy rating and $38.90 price target on its shares.