How to modify the attribute image size ?

Hello,

Thank you for reaching out to us.

Please try to add this code in Theme Options > Theme custom CSS:

.single-product form.cart table.variations td.value select {
    background-color: #0a0a0a;
    color: white;
    font-size: 16px;
}
.single-product form.cart table.variations th.label label,
.single-product .single-product-size-guide span.et-element-label,
.single-product .quantity .quantity-wrapper.type-simple input {
    color: black;
}
.single-product ul.st-swatch-size-large li.type-image {
    width: 60px;
    height: 60px;
}

Let me know if it works for you.

If you need further assistance, feel free to ask—I’m happy to help!

Warm Regards,
The 8Theme Team