There is no frame of reference. Color is a visual sensation, yet you would be forced to describe it using other senses such as smell, hearing, and touch. Only a person who has seen color could envision the color red in any meaningful visual sense. Conclusion God, by definition, is the supreme good, that which fulfills all desire. Man, by his very nature, desires and acts according to those desires.
Man acts to achieve an intended end.
Since that which is good derives its existence from the supreme good, it necessarily follows that man has some idea of what God is, even though this knowledge is imperfect. Anyone who fulfills some desire has an imperfect knowledge of God. Since God is that which fulfills all desire and man by his very nature desires, it also necessarily follows that man can not have complete knowledge of God in this life.