Bonsai Care

Hawaiian Umbrella Trees can tolerate low light conditions, it is ideal for indoor growth. You can leave it outside but not in directly contact with the rays of the sun. You may put it in your window sill just be it has low light conditions.

Try this for proper care of your bonsai tree:

This particular bonsai needs to be watered well about every two to three days. Although you do not need a green thumb to grow a Hawaiian Umbrella Tree, there is a secret to success, which is never to allow the soil to dry completely. In fact, experts recommend you soak the soil until it is thoroughly wet. When you do water, allow enough water so it actually runs out of the container’s drain holes. In addition to frequent watering, this bonsai tree also enjoys an occasional misting.

For fertilizer, the Hawaiian Umbrella Tree should be fed in the springtime with a good, all-around bonsai fertilizer. To maintain the shape of the tree, all you need to do is provide an occasional pruning to keep the miniature shape. Unfortunately, the Hawaiian Umbrella Tree is prone to both disease and insects. Therefore, you should inspect your tree several times a week to look for problems. In most cases, a good spray of the trunk is all you need to keep the tree clean and healthy.

The soil for this tree should be acidic with a pH level between 5.6 and 6.0. In addition, the soil should be mildly alkaline with a pH level of 7.6 to 7.8. When the tree blooms, you will enjoy a magnificent red color, usually in late winter and early spring, although it can bloom in mid spring as well. Keep in mind that all parts of the Hawaiian Umbrella Tree are poisonous if ingested. Therefore, you always want to keep the plant out of reach of pets and children. Finally, you can propagate the Hawaiian Umbrella Tree with softwood cuttings and seeds, which would need to be sown immediately, as they do not store well.

For more infos, check these out:
http://www.articlesbase.com/gardening-articles/bonsai-care-the-hawaiian-umbrella-tree-22193.html
http://www.bonsaigardener.org/hawaiian-ubrella-bonsai.html
References :

Your tree sounds like its fine. Schefflera arboricola is the proper name for your tree in case you need to look up anything else.

The new growth on these is always a much lighter green color. They will also be smaller and not as well defined in shape. If it is a young plant, most all of the new growth will be at the top. You'll eventually see the same kind of growth from developing branches.

The Schefflera is a tropical plant. That is why it is called an "indoor" bonsai. It needs to be protected from temperatures much below 50 degrees F. All plant grow best outdoors. It's where they live So if you can, and as the weather allows, keep you plant outside. Just keep it out of full direct sun, it can't handle that. Also know it will dry out much faster outdoors.
Indoors will be OK for the tree. I would try to keep it in a bright location. One way to tell if it is doing OK inside would be to watch for "elongation" or "leggy" growth. This happens when the plant is not getting enough light. The spaces between the leaf stems (called "nodes") will get longer and longer as it reaches up for more light. While this is not really that bad, it doesn't help with keeping the bonsai style.

Also, as the leaves get older and the plant develops, the leaves will eventually die off as the "trunk" of the tree forms. First they will turn yellow, then brown, then fall off. This is normal, as long as it's not happening to the entire plant. You'll find that new branches will develop from where the leaf stems came out from the trunk.
References :
Bonsai grower 15yrs+