Three units of SH963 are installed side by side but have problems with colors matching. Is there any easy way to do color matching?

Yes, there is one easy way and does not need any equipment. Picture mode should be set as the same for all 3 units. Choose the unit with the less brightness and color as the standard unit and to adjust the other two units to be closed to the standard unit. Please follow the following steps.
(1) Display a pure white screen (for example, to display a powerpoint new slide)
(2) Go into OSD menu
(3) Picture → Advanced → Color Temperature → set to User (1,2,3, one of them)
(4) Go to Color temperature User X Fine Tuning
(5) Select the color you wish and try to make the color temperature of the other two units to look like the standard unit. This will need to take some time and try and error to make the color of each unit to be close to identical.
(6) Go to Picture → Basic page and select Contrast
(7) Lower the contrast of the other two units to make the brightness to be close to the standard unit