Second one seems perfectly fine to me. In both cases you could substitute “me” for “myself”, so “myself” is used for emphasis, rather than as a reflexive pronoun.
2nd one is certainly wrong. You can’t use myself without referring to yourself at all, that much is clear. To use “myself” on the 2nd one it would have to be rephrased to something like “Members of the yellow team will work afternoons plus I will myself.”
I wasn’t asking for a rephrase, it’s easy to make it unambiguously correct. I was looking for whether the first one was correct, not a better way to phrase it.
Using Myself in Place of I or Me: Usage Guide Myself is often used where I or me might be expected:
as subject
to wonder what myself will say — Emily Dickinson
others and myself continued to press for the legislation
after as, than , or like
an aversion to paying such people as myself to tutor
was enough to make a better man than myself quail old-timers like myself
and as object.
now here you see myself with the diver
for my wife and myself it was a happy time
Such uses almost always occur when the speaker or writer is referring to himself or herself as an object of discourse rather than as a participant in discourse. The other reflexive personal pronouns are similarly but less frequently used in the same circumstances. Critics have frowned on these uses since about the turn of the century, probably unaware that they serve a definite purpose. Users themselves are as unaware as the critics—they simply follow their instincts. These uses are standard.
Both of your examples fall under this description. You’re trying to shoehorn one of them into a more restrictive standard usage simply because you feel only one of them is wrong.
FWIW my attitude is that a reflexive pronoun is used only when the noun or pronoun directly referred to has appeared in the sentence. E.g. John/he shaves himself every morning. I sat myself in front of the computer to read SDMB. So, I speaking only for myself, would not use either sentence. Arguably you have referred indirectly to yourself in the first, but not the second sentence. But of course YMMV.
Added edit:
Notice that had I said above, “Speaking for myself, I…” so the rule I gave isn’t even quite the one I use.
“Myself” is the victim of overcorrection in the examples in the OP and also emails I have received, such as, “If you have questions, contact the Director of HR or myself.” In the OP both examples should be “me.”
However, it’s common for a sentence to have a pronoun near the beginning, only to have its antecedent appear later in the same sentence. Example:
"In her recent article, Jennifer Rubin argued that . . . "
Myself, I (arrrghhh!) find such sentences hard to parse, and they are a pet peef that I have. When I see the phrase “In her recent article” and have not yet seen the antecedent in a previous sentence, I immediately wonder “In whose recent article?”