Crafting light gray dye with glass blocks gives gray glass, rather than light gray glass. This seems to have been introduced in the latest snapshot (14w17a) while the immediately preceding snapshot (14w11b) did not have this issue.
Linked issues
Comments 2
Duplicate of MC-53580 - If you have not, please use the search function in the future, to see if your bug has already been submitted. If you could not find the original report, please comment with the keywords you searched for.
Duplicate of MC-53580