Answer: New growth on Euonymus kiautschovicus 'Manhattan' will be brighter green than older growth. The color can also be affected by light conditions and to some extent by soil conditions as well as by overall health of the plant. If you are certain the original you already have is this same plant -- Euonymus kiautschovicus 'Manhattan' -- then they should match after a year or so of growing in similar conditions.
If you are not sure what your original plant really is, one way to achieve an exact match is to root tip cuttings from it and plant those. Or, you could replace the original and thus be certain you have a match with the new plants.
I should mention that I would suggest you wait until spring to purchase and plant them. Planting evergreens, especially broad leafed evergreens, in late fall can lead to excessive winter damage because the plants are not well rooted before the coldest weather sets in.
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