Grouping discount products in cart by attributes in PrestaShop 1.5

[Kaluza]

Hello,

 

I have PrestaShop 1.5. I want to grouping discount products in cart by attributes "color"

I have product "T-SHIRT" in 3 colors.

 

- color RED price: $1.00 from 1 to 50 pieces, $0.90 from 51 to 100 pieces.

- color BLUE price:  $1.00 from 1 to 50 pieces, $0.90 from 51 to 100 pieces.

- color WHITE price:  $0.80 from 1 to 50 pieces, $0.50 from 51 to 100 pieces.

 

When I have in cart only one color and size, it works good. But now i add two sizes:

 

CART:

 

- T-SHIRT RED S  x 80 p. <--- PrestaShop gets $0.90 price - works good.

- T-SHIRT RED M  x 10 p. <--- PrestaShop gets $1.00 price - I want $0.90

- T-SHIRT RED L  x 10 p. <--- PrestaShop gets $1.00 price - I want $0.90

- T-SHIRT BLUE XS x 10 p. <--- PrestaShop gets $1.00 price - works good.

 

I want get discount price for color. Anyone can help?