For Slavs, Belbog (Belobog) or the White God is a stark opposite to Crnbog (Crnobog), the Black God, depicting the ever-lasting battle between darkness and light, and day and night. While Crnbog is more of a Devil, or the evil demonic God, the White God is the pure opposite – the Creator of light, the bringer of the good and wealth.
Belbog was mostly a part of the Slavic cult in Bulgaria, Poland and Russia. Belbog is apparently very similar, if not the exact equivalent to Svetovid. Svetovid is the God of Spring and Daylight. Belbog primarily represents the side of everything good, light and day, battling the evil, darkness and night. Slavs used to experience the changing of the day and night as the battle of darkness and light, the evil and the good, so naturally, they used personification, turning the common natural cycle into demons and gods – in this case Crnbog and Belbog.
The Slavs, just as all pagans, had to find a way to explain natural cycles like wind, earthquakes, floods, water, fire, Sun, changing of the night and day, etc. so they were explaining all these cycles by personification, establishing gods and demons. They explained the changing of the day and night by representing the day as Belbog and night as Crnbog. Every time the night comes, they believed that the doors of evil are open and thus all humans become more vulnerable, so they greeted every dawn as a blessing and victory of the good – Belbog.
In some Slavic civilizations, before they would start eating, they would always thank t Higher God (in some civilizations Perun, in other Svarog), Koledo and finally the Belbog.
Slavs used to justify every good thing with good influence of the Belbog, and if anything bad happened, they would blame the Crnbog, cursing him and praying for Belbog’s victory. The resemblance between later Christian one God and Devil is obvious.
It was also believed that heavens actually contain the good and evil – day and night, through immortal personification of Belbog and Crnbog, the Black God and the White God with their ever-lasting battle, but Svarog as the Higher God would have authority over each. They believed that when autumn comes, everyone should greet it and be thankful for good harvest, believing that people who would not feel that way were poisoned by Crnbog’s black thoughts and the others were blessed by Belbog.
Belbog, or commonly called Belobog or Belibog literally means the White God. White would then represent the light and everything good, as well as complete opposite to the darkness and everything bad. In some parts of the Slavic culture, considering that light and white are directly connected to day and thus associated with Sun, Belbog was also considered to be the God of Sun and light, while in other Slavic lands he was respected and worshiped as one of the high ranked Gods, besides Svarog and Perun, who was represented as the giver of wealth and light.
Belbog is only hypothetical god. There is no source mentioning him. And your ”Koledo” is definetely not a god. It’s just a different name for kračun (korochun), an old Slavs pagan festival of the winter solstice.