Christ the Son of God - the ultimate revelation of God reveals in the New Testament the truth about the Three-One God?
God - loving and merciful Father (what is the essence of fatherhood?) - Matthew 6:14, Matthew 6:32, Matthew 7:11, Matthew 18:19, Lk 6:36, Lk 11:13, Lk 12:30, Jn 16 27
God – Son Saviour and Redeemer (what is the essence of sonship?) - Lk 19:10, Jn 3:17, Jn 12:42
God - the sanctifying and comforting Spirit of God (God's love has been poured into our hearts Romans 5:5) sent by the Father and the Son - John 14:26, John 15:26, John 16:13
Father, Son and Spirit are one - John 10:30, John 10:38, John 14:10-11
Person - (πρόσωπον [Greek - prosopon], Lat. Persona) - originally, both in Greek and Latin word meant "mask", which was assumed by the actors in the ancient theater. One actor to represent the various characters could in turn assume many masks.
See more at:
Peter Jaroszyński, "A person: from the mask to self", http://www.ptta.pl/lsf/publikacje/osoba.pdf
Latin persona - Boethius (480-524) in the treaty "On the person of Christ and His two natures" gives the classic definition of a person: individua substantia rationalis naturae - individual substance of the rational nature.
God has only one nature: "Deus Caritas est" 1 John 4:8, Ipsum Esse subsistens (Asseitas Self-subsistent Act of Existence, Subsistent Act of Existing Itself) - Thomas Aquinas.
see more: St. Thomas Aquinas’s Concept of Ipsum Esse Subsistens - http://catholic-church.org/grace/ecu/3/Chapter2.pdf
Can we say that God is "three individual substances of the same nature"?
In God there is no difference. The Father has no origin, the only begotten Son is eternally generated by the Father, the Spirit is the gift of the Father and of the Son, He is the embodiment of Their mutual love - "Deus Caritas est" 1 John 4:8.