Pointed Discussion

Seems somewhat practical, but it truthfully isn't when you take the risk of giving your opponents creatures the bonus as well.

Good vs damage-based sweepers and targeted spells, sometimes lets your troops go through unchecked. Has some more exotic uses like casting it on an enemy creature to prevent the opponent from enchanting it. Thought-provoking multi-functional card. Me like.
And from the flavour standpoint, it Illustrates the white side of Boros pretty well. Your virtues protect you.

Good at making your hybrid and gold boros deck mostly unblockable against mostly one color or other hybrid and gold decks.

Radiance is just so damn /good/.

Shouldn't the rules text just read, "choose a color. Target creature and all creatures that share a color with it gain protection from the chosen color until end of turn." It's like an instant saying "Fear - Target creature cannot be blocked except by black or artifact creatures until end of turn." Right?

@Themlsna: Your first question seems based on grammar, so I'm not an expert on that, but I can answer the Magic question. This isn't like granting fear at all, not even like intimidate (which is fear but for any color and not just black); as fear and intimidate are on cards of a certain color (fear for black, anything else for intimidate) and make those creatures blockable only by artifact creatures or creatures that share a color with it. Bathe in Light though could be cast on, say, a Boros Swiftblade to give it protection from black, so it can't be blocked by black creatures, but could still be blocked by creatures that share a color with it. If, using the Swiftblade as an example again, the creatures were given protection from red, then they couldn't be blocked by red creatures, which would be the opposite of intimidate.

Besides, as mentioned by Helianthus, this card as much more applications than evasion. Sure, going against a deck that's heavy in a color or just happens to have creatures all sharing a color on the field, this card can give your creatures evasion for a turn that might be enough for an endgame move. But the card can act as a Negate on any creatures without shroud; your opponent plays Oblivion Ring, or Lightning Bolt, or Doom Blade and you just target it with Bathe in Light and name the respective color, then your opponent's spells realize they have an illegal target and fizzle. Negated. Though I hadn't considered Helianthus' suggestion of targeting their creature to throw off an enchantment; take that, pesky Totem Auras.