Opening Round Swiss question

In the opening round of a Swiss tournament where the players are divided into two groups, for example 12 players, 1st ranked player plays 7th ranked player, 2nd ranked player plays 8th ranked player etc.

What criteria determines which colour the players receive in the opening round?

Please advise, thank you.

A coin flip determines who gets White on the top board, then the player getting White alternates on the lower boards, between the higher rated player and the lower rated player.

With computerized pairing, I assume the computer would make a random selection for the top board and as you said the other boards rotate the colours. For example, if the highest rated player on board 1 randomly draws white, then the highest rated player on board 2 will play with the black pieces.