Ram Krishna Singh's poem looks at people who try to hide their age. They colour their hair, paint their faces to look younger, and then, oddly, "speak aged lies", which suggests their words are as false as their appearance. The poem leaves open what those lies are, but the phrase hints at a kind of tired, practised dishonesty.
The rainbow of the title seems to stand for this bright, artificial life. Yet the people look up at the sky and try to work out which colour comes after which, before they all blend into one. That image suggests that all the dazzle eventually fades into sameness. The last lines mention beige and indigo, dull and deep shades that "stick their vision", as if the colours they can't use or understand get in the way of how they see.
The speaker sounds quietly critical, even a little amused. The mood is wry and slightly sad, with a sense that pretending can't really change anything.