[SDPhantom]

You need to either remove the function enclosures or call them. I suggest removing them since the functions hooked already exist on load.

-- Включение цвета классов на полосах здоровья
hooksecurefunc("HealthBar_OnValueChanged",function(self)
    local unit=self.unit;
    if UnitIsPlayer(unit) and UnitIsConnected(unit) then
        local _,class=UnitClass(unit);
        if class then
            self:SetStatusBarColor(ColorMixin.GetRGB(CUSTOM_CLASS_COLORS and CUSTOM_CLASS_COLORS[class] or RAID_CLASS_COLORS[class]));
        end
    end
end);
 
-- Изменяет бэкграунд на фреймах таргета и фокуса
hooksecurefunc("TargetFrame_CheckFaction",function(self)
    self.nameBackground:SetVertexColor(0.0, 0.0, 0.0, 0.01);
end);

PS: I cleaned up the code some. Hooking UnitFrameHealthBar_Update() was unnecessary as it ended up triggering HealthBar_OnValueChanged() anyway. Also while RAID_CLASS_COLORS inherits ColorMixin, CUSTOM_CLASS_COLORS isn't so clearly defined as it's not a Blizzard variable. This is why :GetRGB() is called from ColorMixin instead of the color tables. Note '.' was used instead of ':' so the color table could be given to the function as a reference instead of it trying to take ColorMixin as self.