It’s the first time I’ve seen the plant with that dark color, what does it mean? thanks in advance

If you mean the purple in the center of the buds, that’s just a phenotypical expression. Usually shows towards the end of flower bit can show from the beginning.

I agree with Blunt, some plants need cooler temperatures to show their colors, otherwise the purple won’t appear.

Cooler temps is how I always bring out colors. Obviously some just have the genetics but I have 65°f “night time” temps so it makes them all beautiful. My little cheat code.