The Queendom of the Skies by Karen Avellano
Triggered by the death of their grandmother, two siblings find themselves in a fantasy world of unique colours.
In moving to and from Earth to this world of colours, they find that, due to their unique circumstances, they have been chosen to go on a dangerous Quest. It will take them to a dark planet, behind the Earth's moon, where an evil force is threatening to break the Earth's protective layer. The Quest also becomes a transformative one for the children.
The story is contained in two books. Book One - The Magic - deals with the various species of the beautiful world of colours, where light, goodness and care for the environment shine through. Book Two - The Quest - sees the children trying to save the Queen, of the Queendom of the Skies, from the darkness of Tumbra and the coarseness and greed of its reptilian Queen - Gorzolla.
This book can be bought by emailing the author here.