I'm sending the message,I'm not able to see any tick or I'm able to see a different colour yellow.

I'm sending the message,I'm not able to see any tick or I'm able to see a different colour yellow.

 

Please check whether the chat is assigned to a different agent or user. If so, then you are trying to send a message through the notes option. Notes option is for internal comments and it will be saved in the conversation page only and it will not be sent to customer.
Note: Use reply box to send a reply to the customer.