update colors.txt

[anton-tsyganenko]

In minetest 5.0.0:

Unknown nodes:
default:permafrost_with_stones
butterflies:hidden_butterfly_red
butterflies:hidden_butterfly_violet
butterflies:butterfly_red
default:blueberry_bush_leaves
default:blueberry_bush_leaves_with_berries
default:pine_bush_needles
butterflies:hidden_butterfly_white
butterflies:butterfly_white
fireflies:hidden_firefly
butterflies:butterfly_violet
fireflies:firefly

Maybe there are some other new nodes.

[sfan5]

Note that the lack of fireflies: and butterflies: in the colors is intentional.