You must look at the power dissipation in the output transistor that causes it to heat. The max allowed dissipation is 100mW and the datasheet says over the full package temperature range.
As I said on page1, with a 10V supply the typical current into a 3.5V blue or white LED is 17mA so the output transistor dissipates 17mA x 6.5V= 111mW which is OK if the ambient temperature is not too hot.
If an output drives a 2V red LED with 19mA then the output transistor dissipates 19mA x 8V= 152mW which is too hot and a lower supply voltage or a current-limiting resistor is needed.