pick out and put together

I would like to describe the situation below;

There are 4 pairs of cables and each one consists of a coloured one and a white one.
For example, one of the pairs is blue and white and other one is yellow and white. They are somehow inseparable.
Then, what is needed to do is that you put only two white cables together with a tie.

I first wrote that;

Pick out the white cable with the blue one and the one with the yellow one. Then put only these white cables together with a tie.

However, the first sentence seems grammatically wrong and also not describe the situation correctly.

Please give me an idea.
Thanks!

Select the blue and white, and the yellow and white, pairs of cables. Then separate the white cables from the blue and yellow ones, and secure both of these white cables together with a tie.