Digimons in the Digimon Card Game are broadly categorized into 6 colors: each indicating an affinity toward a particular play-style.
The first 3 colors to be introduced were red, blue and yellow, in 54-card Japanese starter decks back in April 2020. When the first booster set [BT-01] New Evolution was released a month later, the forth color, green was introduced. By the release of the second booster [BT-02] Ultimate Power in July 2020, DCG added an black and violet into the game. The Japanese starter decks for green, black and violet are set to be released in November 2020.
Remarks: this guide provides only a generalization and is not a hard rule that applies to all digimons of that color.
Red: powerful and aggresive
Red decks usually setup into strong digimons with high DP and effects such as <DP+?> and <SecurityAttack+?>, allowing them to fearlessly and aggresively attack the (opponent's) security pile. Red decks have access to destuctive digimon effects such as [BT1-23] SkullGreymon and [BT2-018] Volcanicdramon, as well as the powerful removal option card [ST1-16] Terra/Gaia Force. Due to aggressive nature of red decks, they are quite early-game oriented and is quite straightforward to play.
Blue: focused on debuffing, disabling and rapid attacks.
Yellow: it's all about security defense and recovery
Green: efficient and fast digivolutions
Black: the great wall
Violet: rise from the graves
White became a core deck color starting BT-06 when Eosmon was introduced, which prior to that, was reserved for some LV7 Digimons such as Omegamon, Diaboromon and Milleniummon. There is no one particular trait or playstyle for white, and it mostly depends on the archetype you are playing instead.