In the West, the Holy Trinity is often pictured as Jesus the Son, the Father as a rather stereotypical "old man", and the Holy Spirit as a dove. As scripturally based as this is, it doesn't really portray the concept of "3 equal persons in 1 God" as does the typical Eastern depiction.
In the East, the Holy Trinity is most often portrayed as three angels. This comes from the Old Testament story of the Hospitality of Abraham. In Genesis 18, Abraham and Sarah are visited by three "wanderers" who prophesy the birth of Isaac after Abraham offers them hospitality.
The figure on the left represents the Father. We see a very little of a blue garment, which represents the Heavens and alludes to the fact that we do not see the Father directly. Behind the Father we see "the Father's house"; his "mansion" with "many dwellings".
The figure in the middle represents Christ. The dark garment represents the earth and alludes to his humanity. The gold stripe speaks of his kingship. He rests his two fingers on the table to represent his humanity coupled with his divinity. He points to a cup of wine. He also wears a blue garment, representing the Heavens. Behind him is a tree (the tree of life, the wood of the cross.)
The Holy Spirit, on the right, wears the green of new life along with the blue of the heavens. The mountain in the background represents the mountain(s) on which God has often been encountered.
Hat tip to Wellsprings.