For Simon, it appears to be this, at least to me:
-Choice 1 - Castlevania box art
-Choice 2 - Red - Simon's Quest
-Choice 3 - Yellow & Black - Christopher Belmont
-Choice 4 - Red & Black - Castlevania Chronicles Simon
-Choice 5 - Blue - Super Castlevania IV Japanese Box Art
-Choice 6 - Purple (with gray hair) - Vampire Killer Sprite colors (this one is kinda reaching)
-Choice 7 - Orange with Red Hair -
?
-Choice 8 - Dark purple (dark brown hair) -
?
As for Richter:
-Choice 1 - Classic Blue - Rondo of Blood
-Choice 2 - Red - Unused "Red" Richter (Castlevania - The Bloodletting)
-Choice 3 - Purple -
?
-Choice 4 - Green - Poisoned Sprite for Richter (Rondo of Blood)
-Choice 5 - Yellow/Brown, Red Bandanna - Julius Belmont (Sorrow series)
-Choice 6 - Blue with Gray lining - Symphony of the Night
-Choice 7 - Gray - "Slowed Down"/"Petrified" Richter (Rondo of Blood and DraculaXX)
-Choice 8 - White/Red - Leon Belmont (Lament of Innocence).