Starting from ST9 and ST10, multi-color cards and DNA Digivolution are introduced to players. These are new mechanics that help bring the Digimon Card Game to a next level of technique and strategy.
Multicolor Digimon or Option Cards
These Digimon and option cards have multiple colors, such as yellow/purple, blue/green, black/red, blue/red, etc. They are treated as having all the specified colors simultaneously.
Unlike Digimon with effect such as "Your Turn/ All turn: this Digimon is also treated as (color)", multiple colour Digimon are considered to have multi-color in all areas, including raising area, battle area, trash, hand, deck, security stack. Moreover, a single multicolor Digimon counts as having multiple colors for cards that care about color count.
For example: [BT8-053] Raidramon is a blue/green Digimon that is counted as both a blue Digimon and a green Digimon in all the area (including raising area). Since it is a blue/green Digimon, it can digivolve into a Digimon that has either color. If a card effect requires you to have 2 or more colors of Digimon in play, a single multicolour Raidramon counts for 2 colors all by itself.
[BT8-084] Kimeramon is a special white Digimon that can be evolved from any color Digimon. If Kimeramon is Jogress-ed (DNA) Digivolution from other multiple colors Digimon, this Digimon is also treated as the color of the cards in its digivolution cards. For example, if Kimeramon is jogressed from a LV4 yellow/purple Digimon and a LV4 blue/green Digimon, Kimeramon now itself is considered as a 5 colors Digimon (white, yellow, purple, blue and green).
In the early time of ST9/ST10, there are many misplays when using multicolour option cards. Originally we have thought that we could cast a multi-color option card as long as there is at least 1 card of the same color in play, this is INCORRECT.
To use a multi-color option card, you must meet all its color requirements. For example, to use [BT8-105] Dark Gaia Force, you must have both black and red color cards on your field. These can include your hatched Digitama in raising area, tamer or Digimon in battle area.