Yes, you can put an inflatable pool on your artificial lawn. This should not cause any problems. The grass will not discolour or die. However, if there has been a heavy weight pressed down on the grass fibres for a long period of time, the fibres will be matted down. This can be easily fixed by brushing the fibres to rejuvenate them. Of course, you should always make sure the base is strong enough to hold the extra weight when you are planning to place an inflatable pool or another heavy object.