Pine Script for Trading View: How to display on certain time frames

Could you kindly teach me how to not show the vertical line for timeframe of more than or equal to 1 Hour? I desire to show the vertical lines (when the market opens) .

There is a difficulty using the iff statement alongside with the use of the likes of isIntraday and cannot compile.

Thank you in advance.

 //@version=2

study("Line", overlay=true)

t2 = time(period, "1800-1801")
t1 = time(period, "0300-0301")
t3 = time(period, "0930-0931")

Open2 = na(t2) ? na : blue
Open1 = na(t1) ? na : green
Open3 = na(t3) ? na : green