Create a new layer for FLOWERS.
Pick your green colors from the VINE swatch or use your own.
For the flowers, be consistent and use as many of the same reds, blues and yellows found elsewhere in the image as you can. It not only helps keep file size small, it will help the color balance of your painting.
Use the darkest green to base paint some shrubs around the foundation of the house. Just scribble in some shapes with a size 2 paintbrush. We're working on a separate layer, so you can always erase any pixels later that don't look 'just right'. Use a light green to highlight the tops of a few 'shrubs'.
Blue flowers:
These will be tall narrow flower clumps.
Paint a tall group of squiggly light blue lines. Accent with a darker blue squiggle. Paint a few pixels on far left and some more on far right. Maybe a few more near center.
Red flowers:
These will be round or Rose-like.
Use the same red used on vine, paint a circular clump of pixels. Accent on one side with a dark red. Paint a shrub-full group of these near the blue flowers. Have most of the flowers toward the top of the group. Accent a few with pinkish-red or orange-red.
Yellow flowers:
These will be small flowers on tall stems.
Use a medium green from shrubs and draw some straight stem lines wherever you want to place the yellow flowers. Use a 2 pixel brush to stamp a yellow flower here and there along the stems. Use a 1 pixel brush and some dark yellow (gold or orange-yellow) to paint a few accent spots.
White flowers:
These will be daisy-like and must be painted on top of a dark color or they won't show up.
Use a 2 pixel brush and paint 4 dots in shape of + sign. Use the same dark yellow used above to paint a center dot. Copy & paste this 'daisy' on top of the dark green wherever more flowers are needed.