The 3 primary colors of the Light are red (RED), green (GREEN) and blue (BLU), from which the RGB name is; are called "PRIMARY" because, mixed together, they generate the most colors that the human eye can perceive (additive process).
Initially, in the 1970s, the first LEDs were only available in RED and then in GREEN color, and were used as indicators in electronic circuits. Only in the '90s were made of BLUE Light Led, and it was then possible to produce devices that, blending the light between them, could generate any color.
In modern LEDs, White light is generally made with a blue LED coupled to a YELLOW PHOSPHORUS. By adding more amount of RED phosphor, the WHITE tone tends to more HOT WATER, while reducing the tone of the light you get tends more to the Blue, then Cold Light.
The human eye is staggeringly sensitive to being able to perceive small changes in the length of the Chip, which can be caused by the thickness of the phosphorus, its concentration, its composition, and / or the deposition conditions can make great differences;
The difference in tone therefore is not to be considered a defect, but inevitable manufacturing variance.