The simplest approach is to store all of the worksheet data in US format. Of course, that only works if you are simply using the worksheet as a data store and your users do not need direct access to the worksheet to view the data in Google sheets.
Regardless of the worksheet Locale, the values displayed on the client will
be formatted based on the client’s device settings. The US customers see the data in US format. The CO customers see the data
in CO format.
The client always transmits data from and to the server in US format on the “wire”.
When the data arrives at the server, the worksheet Locale controls how the server writes the data to the worksheet. If you can get away with using US Locale for the worksheet, we write the worksheet data in US format.
Another alternative is to use the CO Locale for the worksheet. In that case, the server writes the worksheet data in CO format.
If the worksheet data must be written in different format for the US and CO, then you need two worksheets. Each with its own Locale. This is only necessary if your users need to look at the worksheet data directly in Google sheets and need to see the worksheet data formatted in their preferred Locale format.