Is it possible to make a public variable?

You have two options regarding what you are looking for.

First would be whats we call Global Variables. You can declare a global variable by placing _G. before the name of the variable. You will be able to call this variable from almost any script within your game file.

Script 1:

_G.bool = true -- Creates a global variable and assigns 'true' as the value

Script2:

print (_G.bool) --Should print 'true'

Another option would be to create a Module Script with variables you wish to use in multiple scripts. These work somewhat similar to global variables when you refer to them in other scripts.

Lets say you made a module script returned the array of variables called _M. After you pull the module script into your new script, you can refer to the variables as _M.variable or whatever you named the variable you created in the module script.

Example of module script:

_M = {
    bool = true
}

return _M

How to call the variable in the module script:

_M = require('Path to Module Script') -- This will call the module script and return the variables

print (_M.bool) --This should print 'true'

Let me know if this answers your question.