To view Amazon's sub-variation reviews, you can follow the steps below:

1. Log in to Amazon Seller Center: Open the Amazon Seller Center website and log in with your seller account and password.

2. Enter the product management page: On the homepage of the Seller Center, click the "Inventory" or "Inventory Management" option to enter the product management page.

3. Select a product: On the product management page, find the product you want to view sub-variation reviews for and click the link for that product.

4. Enter the sub-variation page: On the product details page, you can see a list of the main and sub-variations of the product. Click the sub-variation link for which you want to view reviews.

5. View reviews: After entering the sub-variation page, you can see the detailed information and related data of the sub-variation. In the tab at the top of the page, select the "Reviews" or "Evaluations" option to view the reviews of the sub-variation.

Please note that Amazon's review system is written by buyers themselves, so the reviews of sub-variations may be different. Make sure you choose the right sub-variations and carefully read and analyze the customer reviews to understand the strengths and weaknesses of your product.