If they're going for an international story like Kyoryuger, it would be incredibly unrealistic if half of them are Caucasian unless they were biracial natives or a small population of European Caucasians dotting each. However, the chances of every ranger being a single ethnicity or race over another are very close to slim to none.
Since it is a contemporary season , there are as much if not more Eastern Asians in the world today than there are Caucasians [though a majority of Indians and the majority in the Middle East could be identified as Caucasians as the Indo-European sphere stretched from the Isles to India anyways], Black Africans and so on. So therefore, Eastern Asians should make up at least 1/3 to a quarter of the team. Gold being a knight is a given , but then again, there were plenty of Black Africans as well in Medieval Europe, aka Moors. Just make Gold a Moor Knight from Spain and no problem there.
However, if we wanted to go the Battle Fever route, cast 1 person to represent each country/region to be used and it would work.
If they are going down an international route, I can see this:
Red:Far Eastern
Black: Latino or South American.
Blue: Moroccan/ Berber
Green: Hmong/Tibetan or Indian
Pink: Saharan African
Gold:Southeast Asian
Cyan:same as in Japan, preferably. If not, African American.
Navy: Arabian or white South African.
Violet: Latina and Slav, or Slav and Hmong.
If they ditch the international motif mostly, I can see:
Red: White American
Black: Eastern Asian
Blue: Middle Eastern
Green: Maybe another ethnicity?
Pink: Black American or White.
Gold: Caucasian or African Moor.
Cyan:same as in Japan, preferably. If not, Black American.
Navy: Arabian.
Violet: Latina and Slav, or Slav and Hmong.
[HIDE]Samurai never explained how only Mia was Eastern Asian, or the fact of being samurai despite fleeing Japan to presumably intermarrying with at the earliest in the 1800's to: A union soldier or widow [which explains Jayden and Lauren] , a Latina/o Texan rebel, a former slave/ Black slaveowner/freedman and a confederate family [Emily]. Mia is possibly the only family that could have stayed in Japan up until the 1920's or after the War. And even if the samurai did marry like this, I highly doubt any descendants would be able to keep their status unless they were the only ones to survive and therefore, were forced to do that or give it up? If the ancestors of the rangers had the same makeup as their descendants, it becomes problematic with Kevin due to Japanese xenophobia of the time, unless said ancestor was highly liberal for his time and married.
Therefore, we shouldn't really place much logic if a knight becomes Black, Indian or whatever ethnicity and racial combination out there. [/HIDE]