Enhance the green color of begonias

I have one begonia 'cleopatra' and one begonia 'Tiger Kitten'.
They both have some mottled green parts on the brown color leaves.
I prefer the more green leaves and need some suggestions.
I know the light intensity may partly affect the color.
Does lower light environment bring more green color and higher light bring brown color?

Many cultural conditions can affect the color of foliage and blooms. Nutrient toxicities and deficiencies (deficiencies of N, Mg, and Fe in particular), high levels of solubles in the soil, soggy soil, temperature, photo-period/photo-intensity, pH, and others, can all affect bloom and foliage color.

Three different pigments - chlorophyll, flavonoids, and carotenoids - mixed in different proportions, give color to plants. By mixing and matching the three pigments, an endless variety of colors can be created. E.g. most reds are the result of mixing orange carotenoids with magenta flavonoids. Cellular pH (not to be confused with soil pH) has a profound effect on plant color.

Even most experienced gardeners think that lowering soil pH produces blue blooms in hydrangea. Technically, it is only a part of the equation. Lowering soil pH makes aluminum ions more readily available for plant uptake. The aluminum is then available to bond with pigment compounds (anthocyanin, the colored component of flavonoids) changing the way color is reflected. Our perception is blooms changing from pink to blue.

The anthocyanidin group is what makes apples, autumn leaves, roses, strawberries, and cranberries red. They make blueberries, cornflowers, and violets blue. They also make some grapes, blackberries, and red cabbage purple. One of the things that changes the color of anthocyanins is the level of acid or alkali (the pH) in the cell surrounding the pigment. As cellular pH increases, the pigment changes structure and reflects different wavelengths of light. The anthocyanin reflects bright pink in acid cell environments, reddish-purple in neutral and green in more alkaline cells.

I have an Echevereia that wants to be pink, but if I add an Fe chelate to the soil, or if I add vinegar to the irrigation water, it turns an ugly shade of green (think pink mixed with green) within just a few weeks because in both cases, Fe becomes abundantly available. The conclusion is that the plant is pink only when there is (at least a mild) Fe deficiency and the deficiency is pH driven.

There are several types of variegation. One is 'chimeral', and it consists of two genetically different tissue types living side by side on the same (usually) leaf. The other of the two most common types would be pigmental, a condition where one or more pigment masks the presence of other or another pigment. In both cases, the reasons for change I mentioned above could come into play. Lots of variables, as you can see.

Al