Last February, whole Bangkok city was surrounded by this flower.
At first I mistaken this with Lagerstroemia, which bloomed at the same time.

I saw this flowers on the street but couldn't make pictures, for the flower looked not fresh.

Its more spectacular when you see them in distance.

The yellow one is Tabebuia chrysantha, also called Tree of Gold.
I took pictures at Suan Luang Rama IX park, eastern side of Bangkok (near my home).

Pink flowers are Tabebuia rosea or Pink Tacoma, Pink Trumpet Tree.