The Kiznaiver site just posted the official flowers the girls are holding and confirmed their meaning will help us better understand the series.
Nico: Agapanthus474Please respect copyright.ＰＥＮＡＮＡH6gjw3xHKL
Honoka: Zinnia474Please respect copyright.ＰＥＮＡＮＡh33Bu8mfFt
Chidori: China aster474Please respect copyright.ＰＥＮＡＮＡm3klhHzOo6
Noriko: Roses
So I did some Hana kotoba google’ ing. Here’s a brief (second) look at their meaning below the cut!
Nico
The Agapanthus is known as the “flower of love”. Its meanings include 「the arrival of (romantic) love (恋の訪れ)」, 「love letter（ラブレター）」 and 「intellectual attire/guise （知的な装い）」. It’s said that this last meaning comes from the refreshing and delicate appearance of the pale purple/blue flowers. 474Please respect copyright.ＰＥＮＡＮＡKmxc7BzXCi
Source: [x]
Honoka
「thoughts of absent friends（不在の友を思う）」474Please respect copyright.ＰＥＮＡＮＡHMK2eIfP09
「I mourn your absence（あなたの不在を悲しむ）」474Please respect copyright.ＰＥＮＡＮＡgwMjFwInvl
「Don't be off your guard (注意を怠るな)」474Please respect copyright.ＰＥＮＡＮＡ8UitJveL9A
Source: [x]
“Thoughts of friends or thoughts of a missing friend are the most common meanings for the zinnia.“ Yellow zinnias mean “daily remembrance”.474Please respect copyright.ＰＥＮＡＮＡIv216bHNDo
Source: [x]
Chidori
General meaning:474Please respect copyright.ＰＥＮＡＮＡxGLJsWNRtk
• 「Change (変化)」474Please respect copyright.ＰＥＮＡＮＡidGESod0jp
• 「Reminiscence (追憶)」474Please respect copyright.ＰＥＮＡＮＡ64sl0VNUjX
• 「Agreement / Sympathy (同感)」474Please respect copyright.ＰＥＮＡＮＡh8qJs9PlFm
• 「Belief in (romantic) Love (信じる恋)」
Occidental meaning:474Please respect copyright.ＰＥＮＡＮＡUkWT1Za3il
• 「Variety（多様性、変化）」474Please respect copyright.ＰＥＮＡＮＡXKqFGTTScd
• 「Fidelity（忠実、貞節）」474Please respect copyright.ＰＥＮＡＮＡcA1OGLFvIV
• 「I will think of you（私はあなたを想うでしょう）」
Color meaning:474Please respect copyright.ＰＥＮＡＮＡXOXN6jqq1O
• White: 「Please believe me (私を信じてください)」474Please respect copyright.ＰＥＮＡＮＡzU2kkrGmak
• Purple: 「Victory of (romantic) love (恋の勝利)」, 「My love is deeper than yours (私の愛はあなたの愛より深い)」474Please respect copyright.ＰＥＮＡＮＡtuWkozxmL9
Source: [x]
Noriko
It’s hard to tell whether Noriko is holding orange roses or yellow ones, so I’m including both!
General meaning:474Please respect copyright.ＰＥＮＡＮＡQv5asV4gOy
• 「Love (愛)」474Please respect copyright.ＰＥＮＡＮＡg7aavppIL5
• 「Beauty (美)」474Please respect copyright.ＰＥＮＡＮＡlgApsf0N9A
Source: [x]
Color meaning:474Please respect copyright.ＰＥＮＡＮＡqmXFjCZGqS
• White: 「 Purity / Chastity( 純潔)」, 「I am worthy of you (私はあなたにふさわしい)」, 「Deep respect (深い尊敬)」
• Green: 「Calm / Gentle (穏やか)」, 「You can have hope (あなたは希望を持ちえる)」
• Orange: 「Innocence（無邪気）」, 「Bonds / Kizuna （絆）」, 「Healthy（健やか）」, 「Trust / Faith （信頼 ）」.
• Yellow: 「Decrease of love（愛情の薄らぎ）」, 「Jealousy （嫉妬）」, 「Friendship （友情）」, 「Devotion （ 献身 ）」, 「Tired / Weary of (romantic) love （恋に飽きた）」.474Please respect copyright.ＰＥＮＡＮＡwHLqeI9VjA
Source: [x] & [x]
and then Add to home screen.