CD-i member Dyno shared these images about the difference between RGB output and the general composite video output of CD-i players. For most CD-i players, it is possible to mod the player with RGB. For example, Mobius Strip Technologies prepared this CD-i RGB kit for use with your CD-i 450 player.
CD-i is not known for its great video output. CD-i member cdifan about the quality: "I was once involved with a broadcast TV show where they put the actual video output of a CD-i 605 player "on air". The TV technicians were appalled at the quality of the CD-i output signal, esp. in regards to timing. I remember one remarking that it was "bad sh*t, barely good enough for household TV's but nowhere near broadcast quality". A Genlock device had to be used to "clean up" the signal. Of course, they would have needed to use one anyway because the CD-i player had no "SYNC" input..."
CD-i member Retrostuff remarks that there are some small differences in the colours (due to image compression?). "The color difference could also be due to the upscalers settings being different per input, here they are on the built in settting called "game 2".
[Thanks, Dyno, cdifan, Retrostuff]