green tomatoe varieties - how do you know when they are ripe

[MousyMouse]

have a couple of 'green tiger' tomatoe plants indoors. and a couple of fruits on there.
how do I know they are ripe? they have dark green and lighter green stripes.

and on another note, can we move the plants outside? or will they just die?

sorry, translation error, it's 'green zebra'

anyone?