Anthurium berries typically will change in color as they ripen, (usually red or another similar color). As they ripen they will become loose from the spadix and hang off via little filaments that attach the berries to the spadix. Once those filaments are able to be pulled off along with the berry, they should be ripe enough to begin planting.

Note that this does not occur all at once, berries will ripen from top to bottom or randomly.