Thank you for your question and we are happy that you like the macro algae. The colour of the blue Ochtodes depends of the light you provide.
It will turn more greyish when it gets a lot ( too much ) light often. We have the best experiences with full spectrum lighting, around 6500k btw. When the Ochtodes macroalgae gets direct sunlight the algae tends to become more purple. Although this marine algae likes good light it will show a deeper blue colour under  a medium strong light. If you have any further questions don't hesitate to contact us.