If anyone can help me in, dude Mikrotik.
if any sector have more than 15 client I wanna change color directly to another color
The quick answer is you need a “custom probe type” (on left in Dude, under “Probes”) to the count the clients. So you treat >15 as “unavailable”.
The appearance settings (which can come from device or type), control the colors. The color is based on the number of ok/fail/etc state of all probes for the device. So if you add your new “connected client >15” probe, it either be success/fail, and the colors follow the usual logic.
The tricky part is the “custom probe type” – that you’re own your own. 
If there is a single SNMP variable to read to know if you have >15 clients, then creating a probe is easier (docs explain how to read SNMP var for probe). Otherwise, you’d need a function, perhaps several, to find the number of clients. But “Dude Functions” are not anything standard – more like excel formulas (but without an help and old/poor doc and limited examples), but there is theoretically a lot you an do in the Function to get the probe the right data to decide if okay/fail.
Basically for dude to help you here, you need to express it in a probe first. I did something similar to track RSRQ/SINR/etc from LTE modems (and fail in dude if singal below my threshold) – works great/flawless – but was a painful, day-long process to figure it out several years ago because “Functions” to do make the Probe work. Thus the disclaimer.
I’d meant to write up my approach for LTE for a long while… Please see, http://forum.mikrotik.com/t/how-to-track-lte-signal-using-the-dude/163250/1 for at least an example of how to use Probe and Functions.
This one from 2009 had this example to the “number of clients” (you might have to adapt the OIDs as needed):
From what has to be one of the oldest thread I’ve seen (started in 2006): “Probe Thread” - http://forum.mikrotik.com/t/probe-thread/10321/1