È possibile far cambiare colore ad alcune piante innaffiandole con acqua colorata. Ricordo di averlo fatto con i fiori molti anni fa nella scuola elementare di scienze.

Dubito seriamente che questo funzioni con un seme perché il colorante dovrebbe cambiare la struttura genetica del seme.

Farlo con una pianta non cambia effettivamente il colore della pianta, piuttosto la tinge dall'interno attraverso l'assorbimento del colorante nell'acqua. Il processo è reversibile sostituendo l'acqua colorata con acqua pulita.

I processi di assorbimento del liquido e il colore genetico sono diversi.

Originale:Se inietto un seme di pianta o di albero con il colorante, crescerà per essere di quel colore?

No, they won’t.

Perhaps you or your class did the classic experiment of putting a white flower or celery stalk in a glass of water with food colouring added.
The flower or celery then transports the coloured water through the xylem tissue in their stems, and thence into the flower petals (& sepals) and the veins of the leaves.
(The purpose of this experiment is to show how water is drawn up through the stems via capillary action, the food colouring makes the process visible by highlighting the xylem tissue.)
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Injecting dye into a seed
Let’s assume the tree seed is neither too damaged by the injection, nor is negatively affected by the dye itself.
The genetic instructions for how the tree grows, including its natural bark, stem, leaf, and flower colours, are encoded in each cell’s DNA.
The presence of some dye in the seed will not change the DNA.

Also, some [vegetable] seeds are treated with coloured antifungal material. Yet the bean plants and bean pods are still green, not bright pink or blue.

Injecting dye into a plant
I’m not sure what you mean by “a plant”: a shrub, an annual or perennial flower, or bulb that is growing in soil?
If the tip of the injection needle is aimed exactly and inserts dye into xylem tissue, then the dye will be carried to some of the plant.
The dye may be visible, depending upon how much the dye is diluted by the water in the xylem, and over how much surface area the it is deposited. Over time, water is expirated out the leaves and draws more water up from the roots, thus diluting any visible dye effects from the affected area.
In any regard, it would be difficult to get a complete effect, much less a lasting one.
Unlike the white flower cutting, this would not be a permanent change.