Task: Text to Code
Input (English): Step 1: find the chip_model of phone table.
Step 2: find the average Hardware_colours in screen_mode table whose Hardware_colours not one of the results of step 1
Output (English): SELECT Avg ( T1.Hardware_colours ) FROM screen_mode AS T1 WHERE T1.Hardware_colours NOT IN ( SELECT T2.chip_model FROM phone AS T2 )