For my front yard project, I am looking for three trees

1> Large tree for shade (Summer shade & winter sun)
2> Medium size tree
3> Small-medium - Near driveway ornamental tree

Zone 9a (77546, Houston, TX)

I do not want anything which is too much maintenance, or leaves are big or has acorns/pines. I prefer something colorful leaves, flowers etc.

Any suggestions. I am not native to this country so lack local gardening knowledge. I would appreciate the help.

Such trees do not exist in my world.

Crepe Myrtle trees are small-medium and bloom all summer.

For large, Elm or Ash tree?

Now for serious answers.
Red Bud
Sweetgum
Red Maple
Live Oak
Tulip tree

Crepe Myrtle is popular and widely used. You should be able to find them sold various places. Do be sure to check particular kind (cultivar, there are many) as some are bred small these days, and size ranges to some that get very big. Leaves are small, they bloom in summer, but will drop spent blooms for a time. Would be a multi-stemmed tree.

Red bud, is a favorite of mine. Medium size tree. Leaves I would call medium. A number of cultivars, some special leaf color, or shape such as weeping, dark pink most common, some shades of pink or white. Early spring bloom. .Not particularly messy, drops small seed pods. Some say these make too many seedlings.

Sweetgum- Large tree, medium leaves, BEAUTIFUL fall color. Be sure to get sterile cultivar or you will HATE the spiny pods.

Red maple- Large tree, medium leaves, seed pods, seedlings, good fall color.

Live oak- Large tree, small leaves. Popular tree in the South. No 'bloom', fall color a boring brown?

Tulip tree- HUGE tall tree, medium to large leaves. I do not think a good candidate for a yard. Does bloom but not so you'd enjoy on top of a tall tree.

Crabapple or hawthorn, are there sterile ones? If so they would be medium, blooming, non messy, small leaves.

There are some Crepe Myrtles that grow as a single trunk. And there are crabapples that flower without setting fruit. I didn't suggest crabapples because I don't they would do well in Zone 9.

yeah, I am no good climatewise for that location