It's harder to get the darker cedar, AKA the "chocolate" cedar as it's often called.
There is lots of it in the forests, but the big tone wood buyers are calling the shots as to what colored logs the tone wood suppliers are choosing to source. Since the big factories want the most uniform looking color they can get, this is what ends up at places like LMI and other wood sellers, unless they are sourcing from the smaller tone wood sellers, who tend to sell more to luthiers than factories, and we tend to like wood with some character...
It's unfortunate that the big factories are so stuck in this aesthetic vise grip. I have talked to two salvage loggers lately who where selling really nice wood to the factories, and they decided to get out of it and just sell the cedar blocks for shake blocks instead. Nowadays, because Old growth cedar is getting harder to source, they can get just as much money selling the cedar as shake blocks, and they don't have to deal with the picky guitar factories who will not accept any color variation in the wood.
It did not used to be this way. Shake blocks have traditionally been a lower grade than luthier wood, but the shortages of wood, and other factors, have driven the demand for shake blocks up. In 20 years when the cedar is commercially done, those big companies might be regretting they did not buy the colorful wood.
But the color will not affect cross grain stiffness, which is very closely correlated to the amount of perfect quarter. 10 or 15 degrees off quarter and you'll see a big reduction in cross grain stiffness.