My front yard is heavily treed with pines and yews are planted against the house. I know the acidity makes it hard to grom most plants, but I desperately need some color in front of the house. I rent, so removing the trees or shrubs is not an option. Any suggestions?

Impatiens, snapdragons and wallerana will do well and for groundcovers, Bunchberry (Cornus canadensis) and wintergreen (Gaultheria procumbens) will do the trick.

Both of the above are excellent groundcovers for under pines and yews. For non-native plants, try Campanula takesimana (Korean Bellflower) which grows to about 2-3' high and will bloom most of the summer, with fat, pendulous creamy white bells with burgundy markings inside. The latter is a little too rambunctious for good garden soil, but it excels in poor areas of the garden.

I have planted many hostas under pine trees and with great success.; There is a lot of variety in hostas so have a look at a catalogue. I have many different types and all have done well. I have also planted pulmonaria also knows as lungwort. In my opinion nothing is more beautiful that a lungwort. This is one of the first plants to bloom in Spring and the varying colors of the flowers is sensational. Lily of the valley has also done well but Lily of the valley can spread and get out of control. Columbines also do well under my pine trees. I also have a huge bleeding heart that does quite well every year.

Astilbe is a good choice.

If you don't mind putting in a shrub, azaleas love acid soil. If you want annuals, impatiens are really colorful and love the shade. They grow reasonably rapidly too. For perennials I have planted bleeding heart and astilbe. Hostas are great too, but are mostly green (although there are some lovely variegated ones as well).
Good luck!