Granulation tissue appearance is due to -
Granulation tissue is a highly vascularized connective tissue. It is formed when tissue heals by scar formation. It appears pink and granular because of newly formed capillaries present in it.
It also consists of:

Fibroblasts
Residual inflammatory cells
Thrombosed capillaries
Chronic inflammatory cells
Budding ends of capillaries
Densely packed collagen