What are the notes in the Blues Scale in D?

First of all, to be able to learn the Blues Scale for "D", you need to know what is "Blues Scales".

The blues scale consists of the following: Root, b3rd, 4th, #4th, 5th and b7th.

EXAMPLE: F blues Scale = F, Ab, Bb, B, C, Eb, F

When playing a twelve bar blues in the key of Bb, use the Bb blues scale: Bb, Db, Eb, E, F, Ab, Bb
The blues scale can also be used over minor chords when the minor chord is sounded for 2, 4, 8, or 16
measures or longer.

EXAMPLE: If D minor is sounded for eight measures, you may use the D blues scale: D, F,
G, Ab, A, C, D

When playing in minor tonalities you may choose to alternate between the dorian minor and the blues
scale, both having the same root tone.

EXAMPLE: If D minor is sounded for eight measures, play D minor(dorian) or play D blues scale or alternate between the two scale sounds.

The blues scale is used to convey a "Funky," "Down-Home," "Earthy" or "Bluesy" sound/feel.  So, now that we have discussed what is Blues Scales, to answer your question. The D Blues Scale is: D, F, G, Ab, A, C, D