According to Wikipedia, that effect was accomplished differently.
“The parting of the Red Sea was considered the most difficult special effect ever performed up to that time.[37] This effect took about six months of VistaVision filming, and combined scenes shot on the shores of the Red Sea in Egypt, with scenes filmed at Paramount Studios in Hollywood of a huge water tank split by a U-shaped trough, into which approximately 360,000 gallons of water were released from the sides, as well as the filming of a giant waterfall also built on the Paramount backlot to create the effect of the walls of the parted sea out of the turbulent backwash.[38] All of the multiple elements of the shot were then combined in Paul Lerpae’s optical printer, and matte paintings of rocks by Jan Domela concealed the matte lines between the real elements and the special effects elements.[39] “
https://en.wikipedia.org/wiki/The_Ten_Commandments_(1956_film)
Interesting. I saw a documentary which said the Niagara Falls thingy
When I saw this for the first time in the late 1960s, I noticed you could see where the film had been spliced to create several special effects. I noticed that the HD release no longer has these slight off colored gaps.
Same for THE GREATEST SHOW ON EARTH.