Hi Abubakr,
Thank you for using Syncfusion products.
We can change the popups text using Localization. We have prepared sample based on your requirement and it can be downloaded from below link,
Please find the output screen shot from below,
Please find the UG documentation from below,
Based on your previous update, we assume that you want to change the background color of the picker header as highlighted in the below screen shot.
Could you please confirm us whether this is what you have mentioned as "background colour from blue to any other colour" in your update? If yes, currently we do not have support for this. We will let you know when this feature is implemented.
If our understanding is different from your requirement, could you please explain briefly about your requirement? It will be useful for us to investigate further on this and assist you with the better solution at the earliest.
With Regards,
Gayathri R