a large number of possible ACNH Rose color combinations from Lambert Kent's blog

No bloom in Animal Crossing: New Horizons is more elusive and difficult to grow than the Blue Rose, which is a favorite of cross-breeding enthusiasts who want to grow rare flower colors in the game. The Blue Rose can add a vibrant splash of color to any garden, but it takes several generations of cross-breeding to achieve this beautiful coloration. Because of the complex DNA codes of the flowers in the game, as well as a large number of possible Rose color combinations, it can take several weeks or even months for the Blue Rose to bloom.

The items, despite the fact that they do not sell for much money, can be worn as an accessory or used to decorate a player's home or island. Cross-breeding Blue Roses on the island is a must-do for flower enthusiasts and perfectionists alike, and the results are spectacular. Players must exercise caution, however, because, just as in real-world botany, there is always the possibility that the offspring Roses will be the genetically incorrect color and will never be able to produce Blue Roses. Here's how to increase your chances of success and maximize the efficiency with which you grow Blue Roses.

Furthermore, players must carve out a specific area in order to create the necessary checkerboard pattern and provide space for flowers to flourish. It is also possible to return to the same location and repeat the process until Blue Roses eventually spawn. Even with cross-breeding, it is possible that roses will be the wrong color, at least genetically. Players can check and ensure that they have the correct genetically coded colors by using test cross-breds, which are a part of the breeding process, which are available to them.

In Animal Crossing items NMT, a player stands in a garden of White Roses, where one hybrid Purple Rose has spawned, as one of the hybrid Purple Roses.
These are distinct from the naturally occurring Red Roses in the game, and even from the regular hybrid Red Roses that can be found elsewhere. While some guides will simply recommend that you breed hybrid Red Roses from Purple and Orange Roses, using a more complicated breeding technique that includes the special White Rose will increase the likelihood of Blue Roses spawning in your garden. For example,

Players should always grow Roses and other flowers for cross-breeding purposes from purchased seeds, rather than starting from scratch. The DNA sequence of every flower in the game can be found on the game's servers, and flowers found in their natural state on a player's island, a friend's island, or the Mystery Tour island may have already been crossed several times. The flower seed varieties available at Nook's Cranny change on a daily basis, so it may take a few days for players to collect all of the appropriate seeds. The player's island may not grow Roses or may not grow Roses of a specific color, in which case seeds will not be available at Nook's Cranny, no matter how many times the player checks back. To remedy this situation, players should travel to neighboring islands or visit a friend's island in order to obtain the appropriate seeds there.

Cross-breeding two White Roses together has the potential to result in Purple Rose hybrids, but this is not guaranteed. It is recommended that the White Rose seeds be planted in a diagonal, checkerboard pattern with one space between them on all sides, as is the case with all breeding flowers, to encourage them to cross-breed. For the sake of avoiding confusion, players should discard any incorrect Roses that result from cross-breeding. In order to obtain White Roses after Purple Roses have spawned, players should take those Purple Roses and cross them with Yellow Rose seeds. This cross should consistently produce White Roses. Players must then take the White Roses and breed them with the Purple Roses from the previous step in order to obtain new, or better, Purple Roses for breeding.

If the offspring Roses are good for moving the cross-breeding process forward and eventually spawning Blue Roses, the qualifiers "good" and "bad" indicate that they are. It is possible to determine whether or not a particular purple rose variety is good and has the potential to produce Blue Roses by cross-breeding the purple rose with more Yellow Rose seedlings. Poor-quality purple roses in this cross will yield only white roses 100% of the time, whereas good-quality purple roses will yield white and yellow roses equally often.

After that, players must cross the good Purple Roses together in order to grow special White Roses. The bad ones can be thrown away immediately. Players who want to grow a large number of Blue Roses will almost certainly want to grow a large number of special White Roses as well, so they should repeat this process as often as possible to increase their chances of obtaining a Blue Rose in the process.