Wire size

I have short length solid wire from some outside lights. I'd say 14g maybe 16. Is it OK to use for arduino to LCD connection ?

14 or 16 gauge??? Yes you can use that but wouldn't they get too thick to actually solder together and bend in place? You just need signal level wires. Get some 24-28 ga. Stranded wire is easier to bend.

Thanks. They are stiff. Was more wondering if size affects signals. I have yards of phone wire to use too.

No, the gauge affects current-carrying capability, and "fatter" wires have less resistance.

In low-voltage/low-current applications neither of these are of concern and we can assume the resistance is zero.

If you are running several Amps through house wiring, or hundreds of Amps from a car battery, the resistance can result in a voltage-drop, and/or the wires can overheat and burn up if they are too small.

[u]Wire Gauge Chart[/u] showing resistance per 1000 feet or per 1000 meters as well as recommended current-carrying capability.

Use the phone wires for your LCD wires. They are normally 22-24g and perfect for your application and much easier to use.