There is an Fraxinus americana 'Autumn Purple', an ash that supposedly
has especially good purple fall color.

There is a book on Purpleleaf Plums by Arthur Lee Jacobson that
attempted to describe the many cultivars. There are several
purplish/reddish-leaved cultivars of Norway maple including 'Crimson
King', 'Royal Red', 'Crimson Sentry' and 'Goldsworth Purple.'

http://www.msue.msu.edu/imp/modzz/00000026.html

Other red/purplish-leaved trees include the following:

purple beech (Fagus sylvatica purpurea)
purple smoke tree (Cotinus coggygria 'Royal Purple')
purple English oak (Quercus robur 'Atropurpurea')
purple-leaved birch (Betula pendula 'Purpurea')
purpleleaf redbud (Cercis canadensis 'Forest Pansy')
purple filbert (Corylus maxima 'Purpurea')
red Japanese maple (Acer palmatum atropurpureum)

One purple-leaved tree goes a long way in a landscape as an accent
plant. They are often overused.

There is some genetic engineering work to develop better ornamental
plants. For example, their is a commercial effort to transfer blue
genes into flowers that lack blue shades, such as carnation and rose.
The Australian company Florigene has released several "blue" carnation
cultivars such as 'Moondust', 'Moonlite' and 'Moonshadow." However,
they are not true blue.

My Love is Like a Blue, Blue Rose
http://www.biomedcentral.com/news/20030213/06

Florigene
http://www.florigene.com.au/