Gen 1:26 and Gen 1:27 if analyze is perspective based.
In Gen 1:26, the Speaker of the verse is the Word of God or the Image of God who is also the Son. According to John 1:18, Only the Son can see Father ALL THE TIME. In Heb 1:8, the Son who was in the form of God was also called God. Therefore, from the point of view of the speaker, there were 2 of them hence, the use of “US” “OUR”. The Father refers to the Eternal Life John 17:3 who lives in an unapproachable light that no one can see 1 Tim 6:16, He is very vast that fills heaven and earth Jer 23:24. Part of the eternal Life in exact essence is in the Son who is the Image of Eternal Life- Col 1:15. Since all the time only the Son sees the Father, the Son also used plurality in John 17:21 to refer to Him and the Father in the same manner that it was used also in Gen 1:26.
Now, when it came to Gen 1:27, this now is an account coming from the narrator. In the narrator point of view, He only sees one- The Son or the Image of God because He cannot see what the Image of God can see hence, He used “God” and “His” a singular pronoun
“So God created mankind in his own image, in the image of God he created them; male and female he created them.”Genesis 1:27 NIV
Son = Image of God Col 1:15
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