In most of traditional P systems, each rule has the same execution time. That way of using the rules is not quite realistic from a biological point of view, because external conditions always change in an unpredicted manner such that different reaction may take different time to execute. In this work, we investigate the computation efficiency of tissue P systems by removing the restriction that each rule should complete in one time unit. The timed tissue P system is constructed by adding a time mapping to the rules to specify the execution time for each rule.A uniform and time-free solution to 3-coloring problem is proposed, where the execution time of the computational processes involved can vary arbitrarily and the output produced is always the same. In the most of traditional P systems, each rule has the same execution time. That way of using the rules is not quite realistic from a biological point of view, because external conditions always change in an unpredicted manner such that different reactions may take different time to execute. In this work, we investigate the computation efficiency of tissue P systems by removing the restriction that each rule should complete in one time unit. The timed tissue P system is constructed by adding a time mapping to the rules to specify the execution time for each rule. A uniform and time-free solution to 3-coloring problem is proposed, where the execution time of the computational processes involved can vary arbitrarily and the output produced is always the same.